Rigid Body Shape Type (Maya / Unreal 4) - Are capsules the only ones that work?

Hello, I’m using the Physx plugin for Maya v3.4.1 to create Apex cloth for use in Unreal 4.10.4
It’s working great except I can’t get the cloth to collide with the ground. The obvious work around seems to be to create a box type Rigid Body Shape as part of the kinematic ragdoll but it’s not working. It appears that only the capsule type works, which is not good for this purpose because i need something flat.

Am I overlooking something that will make the box type rigid body shape functional?

Thanks!