Complete --mount configuration documentation for service create cmd?

I want to mount a volume using a volume plugin for a swarm service. Is there any complete documentation for configuring the --mount option for the docker service create command? This is what I have going so far, but I know I am defining the driver and driver opts incorrectly:

docker service create --mount type=volume,source=redis-cluster-m1,target=/redis/data/7001/,writable=true,VolumeOptions.DriverConfig.Name=gce,VolumeOptions.DriverConfig.Options.SizeGb=10

I’m using docker engine v1.12-rc2 with experimental features.

SizeGb is relevant to the gce-docker volume plugin.