How do you use custom collision on a skeletal mesh in UE4?

I have a vehicle rig that is a skeletal mesh that imports fine in to unreal but I was wondering how to use a mesh for collision on it. Normally you can just name the collision mesh with UCX_ in front of the name to do it but with skeletal meshes it makes you use a system called phat and I only see cubes/spheres/capsules for collision with that.