diff --git a/openstack/blockstorage/v1/snapshots/requests.go b/openstack/blockstorage/v1/snapshots/requests.go
index f54432f..1bc0a14 100644
--- a/openstack/blockstorage/v1/snapshots/requests.go
+++ b/openstack/blockstorage/v1/snapshots/requests.go
@@ -72,7 +72,7 @@
 	_, res.Err = perigee.Request("POST", createURL(client), perigee.Options{
 		MoreHeaders: client.Provider.AuthenticatedHeaders(),
 		OkCodes:     []int{200, 201},
-		ReqBody:     reqBody,
+		ReqBody:     &reqBody,
 		Results:     &res.Resp,
 	})
 	return res
@@ -102,7 +102,7 @@
 // ListOptsBuilder allows extensions to add additional parameters to the List
 // request.
 type ListOptsBuilder interface {
-	ToVolumeListParams() (string, error)
+	ToSnapshotListString() (string, error)
 }
 
 // ListOpts hold options for listing Snapshots. It is passed to the
@@ -113,8 +113,8 @@
 	VolumeID string `q:"volume_id"`
 }
 
-// ToVolumeListParams formats a ListOpts into a query string.
-func (opts ListOpts) ToVolumeListParams() (string, error) {
+// ToSnapshotListString formats a ListOpts into a query string.
+func (opts ListOpts) ToSnapshotListString() (string, error) {
 	q, err := gophercloud.BuildQueryString(opts)
 	if err != nil {
 		return "", err
@@ -127,7 +127,7 @@
 func List(client *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
 	url := listURL(client)
 	if opts != nil {
-		query, err := opts.ToVolumeListParams()
+		query, err := opts.ToSnapshotListString()
 		if err != nil {
 			return pagination.Pager{Err: err}
 		}
@@ -180,7 +180,7 @@
 	_, res.Err = perigee.Request("PUT", updateMetadataURL(client, id), perigee.Options{
 		MoreHeaders: client.Provider.AuthenticatedHeaders(),
 		OkCodes:     []int{200},
-		ReqBody:     reqBody,
+		ReqBody:     &reqBody,
 		Results:     &res.Resp,
 	})
 	return res
diff --git a/openstack/blockstorage/v1/volumes/requests.go b/openstack/blockstorage/v1/volumes/requests.go
index dc04732..f46b2b6 100644
--- a/openstack/blockstorage/v1/volumes/requests.go
+++ b/openstack/blockstorage/v1/volumes/requests.go
@@ -87,7 +87,7 @@
 
 	_, res.Err = perigee.Request("POST", createURL(client), perigee.Options{
 		MoreHeaders: client.Provider.AuthenticatedHeaders(),
-		ReqBody:     reqBody,
+		ReqBody:     &reqBody,
 		Results:     &res.Resp,
 		OkCodes:     []int{200, 201},
 	})
@@ -118,7 +118,7 @@
 // ListOptsBuilder allows extensions to add additional parameters to the List
 // request.
 type ListOptsBuilder interface {
-	ToVolumeListParams() (string, error)
+	ToVolumeListString() (string, error)
 }
 
 // ListOpts holds options for listing Volumes. It is passed to the volumes.List
@@ -134,8 +134,8 @@
 	Status string `q:"status"`
 }
 
-// ToVolumeListParams formats a ListOpts into a query string.
-func (opts ListOpts) ToVolumeListParams() (string, error) {
+// ToVolumeListString formats a ListOpts into a query string.
+func (opts ListOpts) ToVolumeListString() (string, error) {
 	q, err := gophercloud.BuildQueryString(opts)
 	if err != nil {
 		return "", err
@@ -147,7 +147,7 @@
 func List(client *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
 	url := listURL(client)
 	if opts != nil {
-		query, err := opts.ToVolumeListParams()
+		query, err := opts.ToVolumeListString()
 		if err != nil {
 			return pagination.Pager{Err: err}
 		}
@@ -197,7 +197,7 @@
 
 // Update will update the Volume with provided information. To extract the updated
 // Volume from the response, call the Extract method on the UpdateResult.
-func Update(client *gophercloud.ServiceClient, id string, opts *UpdateOpts) UpdateResult {
+func Update(client *gophercloud.ServiceClient, id string, opts UpdateOptsBuilder) UpdateResult {
 	var res UpdateResult
 
 	reqBody, err := opts.ToVolumeUpdateMap()
@@ -209,7 +209,7 @@
 	_, res.Err = perigee.Request("PUT", updateURL(client, id), perigee.Options{
 		MoreHeaders: client.Provider.AuthenticatedHeaders(),
 		OkCodes:     []int{200},
-		ReqBody:     reqBody,
+		ReqBody:     &reqBody,
 		Results:     &res.Resp,
 	})
 	return res
diff --git a/openstack/blockstorage/v1/volumetypes/requests.go b/openstack/blockstorage/v1/volumetypes/requests.go
index ff71de1..d4f880f 100644
--- a/openstack/blockstorage/v1/volumetypes/requests.go
+++ b/openstack/blockstorage/v1/volumetypes/requests.go
@@ -9,7 +9,7 @@
 // CreateOptsBuilder allows extensions to add additional parameters to the
 // Create request.
 type CreateOptsBuilder interface {
-	ToVolumeTypeCreateMap() map[string]interface{}
+	ToVolumeTypeCreateMap() (map[string]interface{}, error)
 }
 
 // CreateOpts are options for creating a volume type.
@@ -21,7 +21,7 @@
 }
 
 // ToVolumeTypeCreateMap casts a CreateOpts struct to a map.
-func (opts CreateOpts) ToVolumeTypeCreateMap() map[string]interface{} {
+func (opts CreateOpts) ToVolumeTypeCreateMap() (map[string]interface{}, error) {
 	vt := make(map[string]interface{})
 
 	if opts.ExtraSpecs != nil {
@@ -31,17 +31,24 @@
 		vt["name"] = opts.Name
 	}
 
-	return map[string]interface{}{"volume_type": vt}
+	return map[string]interface{}{"volume_type": vt}, nil
 }
 
 // Create will create a new volume. To extract the created volume type object,
 // call the Extract method on the CreateResult.
 func Create(client *gophercloud.ServiceClient, opts CreateOptsBuilder) CreateResult {
 	var res CreateResult
+
+	reqBody, err := opts.ToVolumeTypeCreateMap()
+	if err != nil {
+		res.Err = err
+		return res
+	}
+
 	_, res.Err = perigee.Request("POST", createURL(client), perigee.Options{
 		MoreHeaders: client.Provider.AuthenticatedHeaders(),
 		OkCodes:     []int{200, 201},
-		ReqBody:     opts.ToVolumeTypeCreateMap(),
+		ReqBody:     &reqBody,
 		Results:     &res.Resp,
 	})
 	return res
diff --git a/openstack/compute/v2/flavors/requests.go b/openstack/compute/v2/flavors/requests.go
index 4b89b1a..469c69d 100644
--- a/openstack/compute/v2/flavors/requests.go
+++ b/openstack/compute/v2/flavors/requests.go
@@ -6,6 +6,12 @@
 	"github.com/rackspace/gophercloud/pagination"
 )
 
+// ListOptsBuilder allows extensions to add additional parameters to the
+// List request.
+type ListOptsBuilder interface {
+	ToFlavorListParams() (string, error)
+}
+
 // ListOpts helps control the results returned by the List() function.
 // For example, a flavor with a minDisk field of 10 will not be returned if you specify MinDisk set to 20.
 // Typically, software will use the last ID of the previous call to List to set the Marker for the current call.
@@ -26,17 +32,26 @@
 	Limit int `q:"limit"`
 }
 
+// ToFlavorListParams formats a ListOpts into a query string.
+func (opts ListOpts) ToFlavorListParams() (string, error) {
+	q, err := gophercloud.BuildQueryString(opts)
+	if err != nil {
+		return "", err
+	}
+	return q.String(), nil
+}
+
 // List instructs OpenStack to provide a list of flavors.
 // You may provide criteria by which List curtails its results for easier processing.
 // See ListOpts for more details.
-func List(client *gophercloud.ServiceClient, opts *ListOpts) pagination.Pager {
+func List(client *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
 	url := listURL(client)
 	if opts != nil {
-		query, err := gophercloud.BuildQueryString(opts)
+		query, err := opts.ToFlavorListParams()
 		if err != nil {
 			return pagination.Pager{Err: err}
 		}
-		url += query.String()
+		url += query
 	}
 	createPage := func(r pagination.LastHTTPResponse) pagination.Page {
 		return FlavorPage{pagination.LinkedPageBase{LastHTTPResponse: r}}
diff --git a/openstack/compute/v2/images/requests.go b/openstack/compute/v2/images/requests.go
index 6ccffc4..d901f6e 100644
--- a/openstack/compute/v2/images/requests.go
+++ b/openstack/compute/v2/images/requests.go
@@ -1,11 +1,18 @@
 package images
 
 import (
-	"github.com/racker/perigee"
 	"github.com/rackspace/gophercloud"
 	"github.com/rackspace/gophercloud/pagination"
+
+	"github.com/racker/perigee"
 )
 
+// ListOptsBuilder allows extensions to add additional parameters to the
+// List request.
+type ListOptsBuilder interface {
+	ToImageListParams() (string, error)
+}
+
 // ListOpts contain options for limiting the number of Images returned from a call to ListDetail.
 type ListOpts struct {
 	// When the image last changed status (in date-time format).
@@ -24,15 +31,24 @@
 	Type string `q:"type"`
 }
 
+// ToImageListParams formats a ListOpts into a query string.
+func (opts ListOpts) ToImageListParams() (string, error) {
+	q, err := gophercloud.BuildQueryString(opts)
+	if err != nil {
+		return "", err
+	}
+	return q.String(), nil
+}
+
 // ListDetail enumerates the available images.
-func ListDetail(client *gophercloud.ServiceClient, opts *ListOpts) pagination.Pager {
+func ListDetail(client *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
 	url := listDetailURL(client)
 	if opts != nil {
-		query, err := gophercloud.BuildQueryString(opts)
+		query, err := opts.ToImageListParams()
 		if err != nil {
 			return pagination.Pager{Err: err}
 		}
-		url += query.String()
+		url += query
 	}
 
 	createPage := func(r pagination.LastHTTPResponse) pagination.Page {
diff --git a/openstack/networking/v2/extensions/external/requests.go b/openstack/networking/v2/extensions/external/requests.go
index afdd428..2f04593 100644
--- a/openstack/networking/v2/extensions/external/requests.go
+++ b/openstack/networking/v2/extensions/external/requests.go
@@ -24,12 +24,15 @@
 }
 
 // ToNetworkCreateMap casts a CreateOpts struct to a map.
-func (o CreateOpts) ToNetworkCreateMap() map[string]map[string]interface{} {
-	outer := o.Parent.ToNetworkCreateMap()
+func (o CreateOpts) ToNetworkCreateMap() (map[string]interface{}, error) {
+	outer, err := o.Parent.ToNetworkCreateMap()
+	if err != nil {
+		return nil, err
+	}
 
-	outer["network"]["router:external"] = o.External
+	outer["network"].(map[string]interface{})["router:external"] = o.External
 
-	return outer
+	return outer, nil
 }
 
 // UpdateOpts is the structure used when updating existing external network
@@ -41,10 +44,13 @@
 }
 
 // ToNetworkUpdateMap casts an UpdateOpts struct to a map.
-func (o UpdateOpts) ToNetworkUpdateMap() map[string]map[string]interface{} {
-	outer := o.Parent.ToNetworkUpdateMap()
+func (o UpdateOpts) ToNetworkUpdateMap() (map[string]interface{}, error) {
+	outer, err := o.Parent.ToNetworkUpdateMap()
+	if err != nil {
+		return nil, err
+	}
 
-	outer["network"]["router:external"] = o.External
+	outer["network"].(map[string]interface{})["router:external"] = o.External
 
-	return outer
+	return outer, nil
 }
diff --git a/openstack/networking/v2/networks/requests.go b/openstack/networking/v2/networks/requests.go
index 39a151a..de34989 100644
--- a/openstack/networking/v2/networks/requests.go
+++ b/openstack/networking/v2/networks/requests.go
@@ -1,9 +1,10 @@
 package networks
 
 import (
-	"github.com/racker/perigee"
 	"github.com/rackspace/gophercloud"
 	"github.com/rackspace/gophercloud/pagination"
+
+	"github.com/racker/perigee"
 )
 
 // AdminState gives users a solid type to work with for create and update
@@ -26,6 +27,12 @@
 	TenantID     string
 }
 
+// ListOptsBuilder allows extensions to add additional parameters to the
+// List request.
+type ListOptsBuilder interface {
+	ToNetworkListString() (string, error)
+}
+
 // ListOpts allows the filtering and sorting of paginated collections through
 // the API. Filtering is achieved by passing in struct field values that map to
 // the network attributes you want to see returned. SortKey allows you to sort
@@ -44,17 +51,29 @@
 	SortDir      string `q:"sort_dir"`
 }
 
+// ToNetworkListString formats a ListOpts into a query string.
+func (opts ListOpts) ToNetworkListString() (string, error) {
+	q, err := gophercloud.BuildQueryString(opts)
+	if err != nil {
+		return "", err
+	}
+	return q.String(), nil
+}
+
 // List returns a Pager which allows you to iterate over a collection of
 // networks. It accepts a ListOpts struct, which allows you to filter and sort
 // the returned collection for greater efficiency.
-func List(c *gophercloud.ServiceClient, opts ListOpts) pagination.Pager {
-	// Build query parameters
-	q, err := gophercloud.BuildQueryString(&opts)
-	if err != nil {
-		return pagination.Pager{Err: err}
+func List(c *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
+	url := listURL(c)
+	if opts != nil {
+		query, err := opts.ToNetworkListString()
+		if err != nil {
+			return pagination.Pager{Err: err}
+		}
+		url += query
 	}
-	u := listURL(c) + q.String()
-	return pagination.NewPager(c, u, func(r pagination.LastHTTPResponse) pagination.Page {
+
+	return pagination.NewPager(c, url, func(r pagination.LastHTTPResponse) pagination.Page {
 		return NetworkPage{pagination.LinkedPageBase{LastHTTPResponse: r}}
 	})
 }
@@ -75,7 +94,7 @@
 // extensions decorate or modify the common logic, it is useful for them to
 // satisfy a basic interface in order for them to be used.
 type CreateOptsBuilder interface {
-	ToNetworkCreateMap() map[string]map[string]interface{}
+	ToNetworkCreateMap() (map[string]interface{}, error)
 }
 
 // CreateOpts is the common options struct used in this package's Create
@@ -83,26 +102,23 @@
 type CreateOpts networkOpts
 
 // ToNetworkCreateMap casts a CreateOpts struct to a map.
-func (o CreateOpts) ToNetworkCreateMap() map[string]map[string]interface{} {
-	inner := make(map[string]interface{})
+func (opts CreateOpts) ToNetworkCreateMap() (map[string]interface{}, error) {
+	n := make(map[string]interface{})
 
-	if o.AdminStateUp != nil {
-		inner["admin_state_up"] = &o.AdminStateUp
+	if opts.AdminStateUp != nil {
+		n["admin_state_up"] = &opts.AdminStateUp
 	}
-	if o.Name != "" {
-		inner["name"] = o.Name
+	if opts.Name != "" {
+		n["name"] = opts.Name
 	}
-	if o.Shared != nil {
-		inner["shared"] = &o.Shared
+	if opts.Shared != nil {
+		n["shared"] = &opts.Shared
 	}
-	if o.TenantID != "" {
-		inner["tenant_id"] = o.TenantID
+	if opts.TenantID != "" {
+		n["tenant_id"] = opts.TenantID
 	}
 
-	outer := make(map[string]map[string]interface{})
-	outer["network"] = inner
-
-	return outer
+	return map[string]interface{}{"network": n}, nil
 }
 
 // Create accepts a CreateOpts struct and creates a new network using the values
@@ -115,7 +131,11 @@
 func Create(c *gophercloud.ServiceClient, opts CreateOptsBuilder) CreateResult {
 	var res CreateResult
 
-	reqBody := opts.ToNetworkCreateMap()
+	reqBody, err := opts.ToNetworkCreateMap()
+	if err != nil {
+		res.Err = err
+		return res
+	}
 
 	// Send request to API
 	_, res.Err = perigee.Request("POST", createURL(c), perigee.Options{
@@ -132,7 +152,7 @@
 // extensions decorate or modify the common logic, it is useful for them to
 // satisfy a basic interface in order for them to be used.
 type UpdateOptsBuilder interface {
-	ToNetworkUpdateMap() map[string]map[string]interface{}
+	ToNetworkUpdateMap() (map[string]interface{}, error)
 }
 
 // UpdateOpts is the common options struct used in this package's Update
@@ -140,23 +160,20 @@
 type UpdateOpts networkOpts
 
 // ToNetworkUpdateMap casts a UpdateOpts struct to a map.
-func (o UpdateOpts) ToNetworkUpdateMap() map[string]map[string]interface{} {
-	inner := make(map[string]interface{})
+func (opts UpdateOpts) ToNetworkUpdateMap() (map[string]interface{}, error) {
+	n := make(map[string]interface{})
 
-	if o.AdminStateUp != nil {
-		inner["admin_state_up"] = &o.AdminStateUp
+	if opts.AdminStateUp != nil {
+		n["admin_state_up"] = &opts.AdminStateUp
 	}
-	if o.Name != "" {
-		inner["name"] = o.Name
+	if opts.Name != "" {
+		n["name"] = opts.Name
 	}
-	if o.Shared != nil {
-		inner["shared"] = &o.Shared
+	if opts.Shared != nil {
+		n["shared"] = &opts.Shared
 	}
 
-	outer := make(map[string]map[string]interface{})
-	outer["network"] = inner
-
-	return outer
+	return map[string]interface{}{"network": n}, nil
 }
 
 // Update accepts a UpdateOpts struct and updates an existing network using the
@@ -164,7 +181,11 @@
 func Update(c *gophercloud.ServiceClient, networkID string, opts UpdateOptsBuilder) UpdateResult {
 	var res UpdateResult
 
-	reqBody := opts.ToNetworkUpdateMap()
+	reqBody, err := opts.ToNetworkUpdateMap()
+	if err != nil {
+		res.Err = err
+		return res
+	}
 
 	// Send request to API
 	_, res.Err = perigee.Request("PUT", getURL(c, networkID), perigee.Options{
diff --git a/openstack/networking/v2/ports/requests.go b/openstack/networking/v2/ports/requests.go
index 0fbb9f2..afa37f5 100644
--- a/openstack/networking/v2/ports/requests.go
+++ b/openstack/networking/v2/ports/requests.go
@@ -1,9 +1,10 @@
 package ports
 
 import (
-	"github.com/racker/perigee"
 	"github.com/rackspace/gophercloud"
 	"github.com/rackspace/gophercloud/pagination"
+
+	"github.com/racker/perigee"
 )
 
 // AdminState gives users a solid type to work with for create and update
@@ -19,6 +20,12 @@
 	Down AdminState = &iFalse
 )
 
+// ListOptsBuilder allows extensions to add additional parameters to the
+// List request.
+type ListOptsBuilder interface {
+	ToPortListString() (string, error)
+}
+
 // ListOpts allows the filtering and sorting of paginated collections through
 // the API. Filtering is achieved by passing in struct field values that map to
 // the port attributes you want to see returned. SortKey allows you to sort
@@ -40,6 +47,15 @@
 	SortDir      string `q:"sort_dir"`
 }
 
+// ToPortListString formats a ListOpts into a query string.
+func (opts ListOpts) ToPortListString() (string, error) {
+	q, err := gophercloud.BuildQueryString(opts)
+	if err != nil {
+		return "", err
+	}
+	return q.String(), nil
+}
+
 // List returns a Pager which allows you to iterate over a collection of
 // ports. It accepts a ListOpts struct, which allows you to filter and sort
 // the returned collection for greater efficiency.
@@ -47,15 +63,17 @@
 // Default policy settings return only those ports that are owned by the tenant
 // who submits the request, unless the request is submitted by an user with
 // administrative rights.
-func List(c *gophercloud.ServiceClient, opts ListOpts) pagination.Pager {
-	// Build query parameters
-	q, err := gophercloud.BuildQueryString(&opts)
-	if err != nil {
-		return pagination.Pager{Err: err}
+func List(c *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
+	url := listURL(c)
+	if opts != nil {
+		query, err := opts.ToPortListString()
+		if err != nil {
+			return pagination.Pager{Err: err}
+		}
+		url += query
 	}
-	u := listURL(c) + q.String()
 
-	return pagination.NewPager(c, u, func(r pagination.LastHTTPResponse) pagination.Page {
+	return pagination.NewPager(c, url, func(r pagination.LastHTTPResponse) pagination.Page {
 		return PortPage{pagination.LinkedPageBase{LastHTTPResponse: r}}
 	})
 }
@@ -71,6 +89,14 @@
 	return res
 }
 
+// CreateOptsBuilder is the interface options structs have to satisfy in order
+// to be used in the main Create operation in this package. Since many
+// extensions decorate or modify the common logic, it is useful for them to
+// satisfy a basic interface in order for them to be used.
+type CreateOptsBuilder interface {
+	ToPortCreateMap() (map[string]interface{}, error)
+}
+
 // CreateOpts represents the attributes used when creating a new port.
 type CreateOpts struct {
 	NetworkID      string
@@ -84,51 +110,54 @@
 	SecurityGroups []string
 }
 
+// ToPortCreateMap casts a CreateOpts struct to a map.
+func (opts CreateOpts) ToPortCreateMap() (map[string]interface{}, error) {
+	p := make(map[string]interface{})
+
+	if opts.NetworkID == "" {
+		return nil, errNetworkIDRequired
+	}
+	p["network_id"] = opts.NetworkID
+
+	if opts.DeviceID != "" {
+		p["device_id"] = opts.DeviceID
+	}
+	if opts.DeviceOwner != "" {
+		p["device_owner"] = opts.DeviceOwner
+	}
+	if opts.FixedIPs != nil {
+		p["fixed_ips"] = opts.FixedIPs
+	}
+	if opts.SecurityGroups != nil {
+		p["security_groups"] = opts.SecurityGroups
+	}
+	if opts.TenantID != "" {
+		p["tenant_id"] = opts.TenantID
+	}
+	if opts.AdminStateUp != nil {
+		p["admin_state_up"] = &opts.AdminStateUp
+	}
+	if opts.Name != "" {
+		p["name"] = opts.Name
+	}
+	if opts.MACAddress != "" {
+		p["mac_address"] = opts.MACAddress
+	}
+
+	return map[string]interface{}{"port": p}, nil
+}
+
 // Create accepts a CreateOpts struct and creates a new network using the values
 // provided. You must remember to provide a NetworkID value.
-func Create(c *gophercloud.ServiceClient, opts CreateOpts) CreateResult {
+func Create(c *gophercloud.ServiceClient, opts CreateOptsBuilder) CreateResult {
 	var res CreateResult
 
-	type port struct {
-		NetworkID      string      `json:"network_id"`
-		Name           *string     `json:"name,omitempty"`
-		AdminStateUp   *bool       `json:"admin_state_up,omitempty"`
-		MACAddress     *string     `json:"mac_address,omitempty"`
-		FixedIPs       interface{} `json:"fixed_ips,omitempty"`
-		DeviceID       *string     `json:"device_id,omitempty"`
-		DeviceOwner    *string     `json:"device_owner,omitempty"`
-		TenantID       *string     `json:"tenant_id,omitempty"`
-		SecurityGroups []string    `json:"security_groups,omitempty"`
-	}
-	type request struct {
-		Port port `json:"port"`
-	}
-
-	// Validate
-	if opts.NetworkID == "" {
-		res.Err = errNetworkIDRequired
+	reqBody, err := opts.ToPortCreateMap()
+	if err != nil {
+		res.Err = err
 		return res
 	}
 
-	// Populate request body
-	reqBody := request{Port: port{
-		NetworkID:    opts.NetworkID,
-		Name:         gophercloud.MaybeString(opts.Name),
-		AdminStateUp: opts.AdminStateUp,
-		TenantID:     gophercloud.MaybeString(opts.TenantID),
-		MACAddress:   gophercloud.MaybeString(opts.MACAddress),
-		DeviceID:     gophercloud.MaybeString(opts.DeviceID),
-		DeviceOwner:  gophercloud.MaybeString(opts.DeviceOwner),
-	}}
-
-	if opts.FixedIPs != nil {
-		reqBody.Port.FixedIPs = opts.FixedIPs
-	}
-
-	if opts.SecurityGroups != nil {
-		reqBody.Port.SecurityGroups = opts.SecurityGroups
-	}
-
 	// Response
 	_, res.Err = perigee.Request("POST", createURL(c), perigee.Options{
 		MoreHeaders: c.Provider.AuthenticatedHeaders(),
@@ -141,6 +170,14 @@
 	return res
 }
 
+// UpdateOptsBuilder is the interface options structs have to satisfy in order
+// to be used in the main Update operation in this package. Since many
+// extensions decorate or modify the common logic, it is useful for them to
+// satisfy a basic interface in order for them to be used.
+type UpdateOptsBuilder interface {
+	ToPortUpdateMap() (map[string]interface{}, error)
+}
+
 // UpdateOpts represents the attributes used when updating an existing port.
 type UpdateOpts struct {
 	Name           string
@@ -151,39 +188,43 @@
 	SecurityGroups []string
 }
 
+// ToPortUpdateMap casts an UpdateOpts struct to a map.
+func (opts UpdateOpts) ToPortUpdateMap() (map[string]interface{}, error) {
+	p := make(map[string]interface{})
+
+	if opts.DeviceID != "" {
+		p["device_id"] = opts.DeviceID
+	}
+	if opts.DeviceOwner != "" {
+		p["device_owner"] = opts.DeviceOwner
+	}
+	if opts.FixedIPs != nil {
+		p["fixed_ips"] = opts.FixedIPs
+	}
+	if opts.SecurityGroups != nil {
+		p["security_groups"] = opts.SecurityGroups
+	}
+	if opts.AdminStateUp != nil {
+		p["admin_state_up"] = &opts.AdminStateUp
+	}
+	if opts.Name != "" {
+		p["name"] = opts.Name
+	}
+
+	return map[string]interface{}{"port": p}, nil
+}
+
 // Update accepts a UpdateOpts struct and updates an existing port using the
 // values provided.
-func Update(c *gophercloud.ServiceClient, id string, opts UpdateOpts) UpdateResult {
-	type port struct {
-		Name           *string     `json:"name,omitempty"`
-		AdminStateUp   *bool       `json:"admin_state_up,omitempty"`
-		FixedIPs       interface{} `json:"fixed_ips,omitempty"`
-		DeviceID       *string     `json:"device_id,omitempty"`
-		DeviceOwner    *string     `json:"device_owner,omitempty"`
-		SecurityGroups []string    `json:"security_groups,omitempty"`
-	}
-	type request struct {
-		Port port `json:"port"`
-	}
-
-	// Populate request body
-	reqBody := request{Port: port{
-		Name:         gophercloud.MaybeString(opts.Name),
-		AdminStateUp: opts.AdminStateUp,
-		DeviceID:     gophercloud.MaybeString(opts.DeviceID),
-		DeviceOwner:  gophercloud.MaybeString(opts.DeviceOwner),
-	}}
-
-	if opts.FixedIPs != nil {
-		reqBody.Port.FixedIPs = opts.FixedIPs
-	}
-
-	if opts.SecurityGroups != nil {
-		reqBody.Port.SecurityGroups = opts.SecurityGroups
-	}
-
-	// Response
+func Update(c *gophercloud.ServiceClient, id string, opts UpdateOptsBuilder) UpdateResult {
 	var res UpdateResult
+
+	reqBody, err := opts.ToPortUpdateMap()
+	if err != nil {
+		res.Err = err
+		return res
+	}
+
 	_, res.Err = perigee.Request("PUT", updateURL(c, id), perigee.Options{
 		MoreHeaders: c.Provider.AuthenticatedHeaders(),
 		ReqBody:     &reqBody,
diff --git a/openstack/networking/v2/subnets/requests.go b/openstack/networking/v2/subnets/requests.go
index a7e6b53..e164583 100644
--- a/openstack/networking/v2/subnets/requests.go
+++ b/openstack/networking/v2/subnets/requests.go
@@ -1,9 +1,10 @@
 package subnets
 
 import (
-	"github.com/racker/perigee"
 	"github.com/rackspace/gophercloud"
 	"github.com/rackspace/gophercloud/pagination"
+
+	"github.com/racker/perigee"
 )
 
 // AdminState gives users a solid type to work with for create and update
@@ -19,6 +20,12 @@
 	Down AdminState = &iFalse
 )
 
+// ListOptsBuilder allows extensions to add additional parameters to the
+// List request.
+type ListOptsBuilder interface {
+	ToSubnetListString() (string, error)
+}
+
 // ListOpts allows the filtering and sorting of paginated collections through
 // the API. Filtering is achieved by passing in struct field values that map to
 // the subnet attributes you want to see returned. SortKey allows you to sort
@@ -39,6 +46,15 @@
 	SortDir    string `q:"sort_dir"`
 }
 
+// ToSubnetListString formats a ListOpts into a query string.
+func (opts ListOpts) ToSubnetListString() (string, error) {
+	q, err := gophercloud.BuildQueryString(opts)
+	if err != nil {
+		return "", err
+	}
+	return q.String(), nil
+}
+
 // List returns a Pager which allows you to iterate over a collection of
 // subnets. It accepts a ListOpts struct, which allows you to filter and sort
 // the returned collection for greater efficiency.
@@ -46,13 +62,15 @@
 // Default policy settings return only those subnets that are owned by the tenant
 // who submits the request, unless the request is submitted by an user with
 // administrative rights.
-func List(c *gophercloud.ServiceClient, opts ListOpts) pagination.Pager {
-	// Build query parameters
-	query, err := gophercloud.BuildQueryString(&opts)
-	if err != nil {
-		return pagination.Pager{Err: err}
+func List(c *gophercloud.ServiceClient, opts ListOptsBuilder) pagination.Pager {
+	url := listURL(c)
+	if opts != nil {
+		query, err := opts.ToSubnetListString()
+		if err != nil {
+			return pagination.Pager{Err: err}
+		}
+		url += query
 	}
-	url := listURL(c) + query.String()
 
 	return pagination.NewPager(c, url, func(r pagination.LastHTTPResponse) pagination.Page {
 		return SubnetPage{pagination.LinkedPageBase{LastHTTPResponse: r}}
@@ -76,6 +94,14 @@
 	IPv6 = 6
 )
 
+// CreateOptsBuilder is the interface options structs have to satisfy in order
+// to be used in the main Create operation in this package. Since many
+// extensions decorate or modify the common logic, it is useful for them to
+// satisfy a basic interface in order for them to be used.
+type CreateOptsBuilder interface {
+	ToSubnetCreateMap() (map[string]interface{}, error)
+}
+
 // CreateOpts represents the attributes used when creating a new subnet.
 type CreateOpts struct {
 	// Required
@@ -92,61 +118,60 @@
 	HostRoutes      []HostRoute
 }
 
-// Create accepts a CreateOpts struct and creates a new subnet using the values
-// provided. You must remember to provide a valid NetworkID, CIDR and IP version.
-func Create(c *gophercloud.ServiceClient, opts CreateOpts) CreateResult {
-	var res CreateResult
+// ToSubnetCreateMap casts a CreateOpts struct to a map.
+func (opts CreateOpts) ToSubnetCreateMap() (map[string]interface{}, error) {
+	s := make(map[string]interface{})
 
-	// Validate required options
 	if opts.NetworkID == "" {
-		res.Err = errNetworkIDRequired
-		return res
+		return nil, errNetworkIDRequired
 	}
 	if opts.CIDR == "" {
-		res.Err = errCIDRRequired
-		return res
+		return nil, errCIDRRequired
 	}
 	if opts.IPVersion != 0 && opts.IPVersion != IPv4 && opts.IPVersion != IPv6 {
-		res.Err = errInvalidIPType
-		return res
+		return nil, errInvalidIPType
 	}
 
-	type subnet struct {
-		NetworkID       string           `json:"network_id"`
-		CIDR            string           `json:"cidr"`
-		Name            *string          `json:"name,omitempty"`
-		TenantID        *string          `json:"tenant_id,omitempty"`
-		AllocationPools []AllocationPool `json:"allocation_pools,omitempty"`
-		GatewayIP       *string          `json:"gateway_ip,omitempty"`
-		IPVersion       int              `json:"ip_version,omitempty"`
-		EnableDHCP      *bool            `json:"enable_dhcp,omitempty"`
-		DNSNameservers  []string         `json:"dns_nameservers,omitempty"`
-		HostRoutes      []HostRoute      `json:"host_routes,omitempty"`
-	}
-	type request struct {
-		Subnet subnet `json:"subnet"`
-	}
+	s["network_id"] = opts.NetworkID
+	s["cidr"] = opts.CIDR
 
-	reqBody := request{Subnet: subnet{
-		NetworkID:  opts.NetworkID,
-		CIDR:       opts.CIDR,
-		Name:       gophercloud.MaybeString(opts.Name),
-		TenantID:   gophercloud.MaybeString(opts.TenantID),
-		GatewayIP:  gophercloud.MaybeString(opts.GatewayIP),
-		EnableDHCP: opts.EnableDHCP,
-	}}
-
+	if opts.EnableDHCP != nil {
+		s["enable_dhcp"] = &opts.EnableDHCP
+	}
+	if opts.Name != "" {
+		s["name"] = opts.Name
+	}
+	if opts.GatewayIP != "" {
+		s["gateway_ip"] = opts.GatewayIP
+	}
+	if opts.TenantID != "" {
+		s["tenant_id"] = opts.TenantID
+	}
 	if opts.IPVersion != 0 {
-		reqBody.Subnet.IPVersion = opts.IPVersion
+		s["ip_version"] = opts.IPVersion
 	}
 	if len(opts.AllocationPools) != 0 {
-		reqBody.Subnet.AllocationPools = opts.AllocationPools
+		s["allocation_pools"] = opts.AllocationPools
 	}
 	if len(opts.DNSNameservers) != 0 {
-		reqBody.Subnet.DNSNameservers = opts.DNSNameservers
+		s["dns_nameservers"] = opts.DNSNameservers
 	}
 	if len(opts.HostRoutes) != 0 {
-		reqBody.Subnet.HostRoutes = opts.HostRoutes
+		s["host_routes"] = opts.HostRoutes
+	}
+
+	return map[string]interface{}{"subnet": s}, nil
+}
+
+// Create accepts a CreateOpts struct and creates a new subnet using the values
+// provided. You must remember to provide a valid NetworkID, CIDR and IP version.
+func Create(c *gophercloud.ServiceClient, opts CreateOptsBuilder) CreateResult {
+	var res CreateResult
+
+	reqBody, err := opts.ToSubnetCreateMap()
+	if err != nil {
+		res.Err = err
+		return res
 	}
 
 	_, res.Err = perigee.Request("POST", createURL(c), perigee.Options{
@@ -159,6 +184,12 @@
 	return res
 }
 
+// UpdateOptsBuilder allows extensions to add additional parameters to the
+// Update request.
+type UpdateOptsBuilder interface {
+	ToSubnetUpdateMap() (map[string]interface{}, error)
+}
+
 // UpdateOpts represents the attributes used when updating an existing subnet.
 type UpdateOpts struct {
 	Name           string
@@ -168,35 +199,40 @@
 	EnableDHCP     *bool
 }
 
+// ToSubnetUpdateMap casts an UpdateOpts struct to a map.
+func (opts UpdateOpts) ToSubnetUpdateMap() (map[string]interface{}, error) {
+	s := make(map[string]interface{})
+
+	if opts.EnableDHCP != nil {
+		s["enable_dhcp"] = &opts.EnableDHCP
+	}
+	if opts.Name != "" {
+		s["name"] = opts.Name
+	}
+	if opts.GatewayIP != "" {
+		s["gateway_ip"] = opts.GatewayIP
+	}
+	if len(opts.DNSNameservers) != 0 {
+		s["dns_nameservers"] = opts.DNSNameservers
+	}
+	if len(opts.HostRoutes) != 0 {
+		s["host_routes"] = opts.HostRoutes
+	}
+
+	return map[string]interface{}{"subnet": s}, nil
+}
+
 // Update accepts a UpdateOpts struct and updates an existing subnet using the
 // values provided.
-func Update(c *gophercloud.ServiceClient, id string, opts UpdateOpts) UpdateResult {
-	type subnet struct {
-		Name           *string     `json:"name,omitempty"`
-		GatewayIP      *string     `json:"gateway_ip,omitempty"`
-		DNSNameservers []string    `json:"dns_nameservers,omitempty"`
-		HostRoutes     []HostRoute `json:"host_routes,omitempty"`
-		EnableDHCP     *bool       `json:"enable_dhcp,omitempty"`
-	}
-	type request struct {
-		Subnet subnet `json:"subnet"`
-	}
-
-	reqBody := request{Subnet: subnet{
-		Name:       gophercloud.MaybeString(opts.Name),
-		GatewayIP:  gophercloud.MaybeString(opts.GatewayIP),
-		EnableDHCP: opts.EnableDHCP,
-	}}
-
-	if len(opts.DNSNameservers) != 0 {
-		reqBody.Subnet.DNSNameservers = opts.DNSNameservers
-	}
-
-	if len(opts.HostRoutes) != 0 {
-		reqBody.Subnet.HostRoutes = opts.HostRoutes
-	}
-
+func Update(c *gophercloud.ServiceClient, id string, opts UpdateOptsBuilder) UpdateResult {
 	var res UpdateResult
+
+	reqBody, err := opts.ToSubnetUpdateMap()
+	if err != nil {
+		res.Err = err
+		return res
+	}
+
 	_, res.Err = perigee.Request("PUT", updateURL(c, id), perigee.Options{
 		MoreHeaders: c.Provider.AuthenticatedHeaders(),
 		ReqBody:     &reqBody,
diff --git a/openstack/objectstorage/v1/containers/requests.go b/openstack/objectstorage/v1/containers/requests.go
index afe7c7f..ce3f540 100644
--- a/openstack/objectstorage/v1/containers/requests.go
+++ b/openstack/objectstorage/v1/containers/requests.go
@@ -15,12 +15,12 @@
 // ListOpts is a structure that holds options for listing containers.
 type ListOpts struct {
 	Full      bool
-	Limit     int     `q:"limit"`
-	Marker    string  `q:"marker"`
-	EndMarker string  `q:"end_marker"`
-	Format    string  `q:"format"`
-	Prefix    string  `q:"prefix"`
-	Delimiter [1]byte `q:"delimiter"`
+	Limit     int    `q:"limit"`
+	Marker    string `q:"marker"`
+	EndMarker string `q:"end_marker"`
+	Format    string `q:"format"`
+	Prefix    string `q:"prefix"`
+	Delimiter string `q:"delimiter"`
 }
 
 // ToContainerListParams formats a ListOpts into a query string and boolean
@@ -66,7 +66,7 @@
 // CreateOptsBuilder allows extensions to add additional parameters to the
 // Create request.
 type CreateOptsBuilder interface {
-	ToContainerCreateParams() (map[string]string, error)
+	ToContainerCreateMap() (map[string]string, error)
 }
 
 // CreateOpts is a structure that holds parameters for creating a container.
@@ -82,8 +82,8 @@
 	VersionsLocation  string `h:"X-Versions-Location"`
 }
 
-// ToContainerCreateParams formats a CreateOpts into a map of headers.
-func (opts CreateOpts) ToContainerCreateParams() (map[string]string, error) {
+// ToContainerCreateMap formats a CreateOpts into a map of headers.
+func (opts CreateOpts) ToContainerCreateMap() (map[string]string, error) {
 	h, err := gophercloud.BuildHeaders(opts)
 	if err != nil {
 		return nil, err
@@ -100,7 +100,7 @@
 	h := c.Provider.AuthenticatedHeaders()
 
 	if opts != nil {
-		headers, err := opts.ToContainerCreateParams()
+		headers, err := opts.ToContainerCreateMap()
 		if err != nil {
 			res.Err = err
 			return res
@@ -135,7 +135,7 @@
 // UpdateOptsBuilder allows extensions to add additional parameters to the
 // Update request.
 type UpdateOptsBuilder interface {
-	ToContainerUpdateParams() (map[string]string, error)
+	ToContainerUpdateMap() (map[string]string, error)
 }
 
 // UpdateOpts is a structure that holds parameters for updating, creating, or
@@ -152,8 +152,8 @@
 	VersionsLocation       string `h:"X-Versions-Location"`
 }
 
-// ToContainerUpdateParams formats a CreateOpts into a map of headers.
-func (opts UpdateOpts) ToContainerUpdateParams() (map[string]string, error) {
+// ToContainerUpdateMap formats a CreateOpts into a map of headers.
+func (opts UpdateOpts) ToContainerUpdateMap() (map[string]string, error) {
 	h, err := gophercloud.BuildHeaders(opts)
 	if err != nil {
 		return nil, err
@@ -171,7 +171,7 @@
 	h := c.Provider.AuthenticatedHeaders()
 
 	if opts != nil {
-		headers, err := opts.ToContainerUpdateParams()
+		headers, err := opts.ToContainerUpdateMap()
 		if err != nil {
 			res.Err = err
 			return res
diff --git a/openstack/objectstorage/v1/objects/requests.go b/openstack/objectstorage/v1/objects/requests.go
index 77b8380..f6e355d 100644
--- a/openstack/objectstorage/v1/objects/requests.go
+++ b/openstack/objectstorage/v1/objects/requests.go
@@ -19,13 +19,13 @@
 // ListOpts is a structure that holds parameters for listing objects.
 type ListOpts struct {
 	Full      bool
-	Limit     int     `q:"limit"`
-	Marker    string  `q:"marker"`
-	EndMarker string  `q:"end_marker"`
-	Format    string  `q:"format"`
-	Prefix    string  `q:"prefix"`
-	Delimiter [1]byte `q:"delimiter"`
-	Path      string  `q:"path"`
+	Limit     int    `q:"limit"`
+	Marker    string `q:"marker"`
+	EndMarker string `q:"end_marker"`
+	Format    string `q:"format"`
+	Prefix    string `q:"prefix"`
+	Delimiter string `q:"delimiter"`
+	Path      string `q:"path"`
 }
 
 // ToObjectListParams formats a ListOpts into a query string and boolean
@@ -222,7 +222,7 @@
 // CopyOptsBuilder allows extensions to add additional parameters to the
 // Copy request.
 type CopyOptsBuilder interface {
-	ToObjectCopyParams() (map[string]string, error)
+	ToObjectCopyMap() (map[string]string, error)
 }
 
 // CopyOpts is a structure that holds parameters for copying one object to
@@ -235,8 +235,8 @@
 	Destination        string `h:"Destination,required"`
 }
 
-// ToObjectCopyParams formats a CopyOpts into a map of headers.
-func (opts CopyOpts) ToObjectCopyParams() (map[string]string, error) {
+// ToObjectCopyMap formats a CopyOpts into a map of headers.
+func (opts CopyOpts) ToObjectCopyMap() (map[string]string, error) {
 	if opts.Destination == "" {
 		return nil, fmt.Errorf("Required CopyOpts field 'Destination' not set.")
 	}
@@ -255,7 +255,7 @@
 	var res CopyResult
 	h := c.Provider.AuthenticatedHeaders()
 
-	headers, err := opts.ToObjectCopyParams()
+	headers, err := opts.ToObjectCopyMap()
 	if err != nil {
 		res.Err = err
 		return res
@@ -277,7 +277,7 @@
 // DeleteOptsBuilder allows extensions to add additional parameters to the
 // Delete request.
 type DeleteOptsBuilder interface {
-	ToObjectDeleteParams() (string, error)
+	ToObjectDeleteString() (string, error)
 }
 
 // DeleteOpts is a structure that holds parameters for deleting an object.
@@ -285,8 +285,8 @@
 	MultipartManifest string `q:"multipart-manifest"`
 }
 
-// ToObjectDeleteParams formats a DeleteOpts into a query string.
-func (opts DeleteOpts) ToObjectDeleteParams() (string, error) {
+// ToObjectDeleteString formats a DeleteOpts into a query string.
+func (opts DeleteOpts) ToObjectDeleteString() (string, error) {
 	q, err := gophercloud.BuildQueryString(opts)
 	if err != nil {
 		return "", err
@@ -300,7 +300,7 @@
 	url := deleteURL(c, containerName, objectName)
 
 	if opts != nil {
-		query, err := opts.ToObjectDeleteParams()
+		query, err := opts.ToObjectDeleteString()
 		if err != nil {
 			res.Err = err
 			return res
@@ -320,7 +320,7 @@
 // GetOptsBuilder allows extensions to add additional parameters to the
 // Get request.
 type GetOptsBuilder interface {
-	ToObjectGetParams() (string, error)
+	ToObjectGetString() (string, error)
 }
 
 // GetOpts is a structure that holds parameters for getting an object's metadata.
@@ -329,8 +329,8 @@
 	Signature string `q:"signature"`
 }
 
-// ToObjectGetParams formats a GetOpts into a query string.
-func (opts GetOpts) ToObjectGetParams() (string, error) {
+// ToObjectGetString formats a GetOpts into a query string.
+func (opts GetOpts) ToObjectGetString() (string, error) {
 	q, err := gophercloud.BuildQueryString(opts)
 	if err != nil {
 		return "", err
@@ -345,7 +345,7 @@
 	url := getURL(c, containerName, objectName)
 
 	if opts != nil {
-		query, err := opts.ToObjectGetParams()
+		query, err := opts.ToObjectGetString()
 		if err != nil {
 			res.Err = err
 			return res
@@ -365,7 +365,7 @@
 // UpdateOptsBuilder allows extensions to add additional parameters to the
 // Update request.
 type UpdateOptsBuilder interface {
-	ToObjectUpdateParams() (map[string]string, error)
+	ToObjectUpdateMap() (map[string]string, error)
 }
 
 // UpdateOpts is a structure that holds parameters for updating, creating, or deleting an
@@ -380,8 +380,8 @@
 	DetectContentType  bool   `h:"X-Detect-Content-Type"`
 }
 
-// ToObjectUpdateParams formats a UpdateOpts into a map of headers.
-func (opts UpdateOpts) ToObjectUpdateParams() (map[string]string, error) {
+// ToObjectUpdateMap formats a UpdateOpts into a map of headers.
+func (opts UpdateOpts) ToObjectUpdateMap() (map[string]string, error) {
 	h, err := gophercloud.BuildHeaders(opts)
 	if err != nil {
 		return nil, err
@@ -398,7 +398,7 @@
 	h := c.Provider.AuthenticatedHeaders()
 
 	if opts != nil {
-		headers, err := opts.ToObjectUpdateParams()
+		headers, err := opts.ToObjectUpdateMap()
 		if err != nil {
 			res.Err = err
 			return res