[ODE] Trying to create hollow objects

[m1ke0]

All,

I'm trying to build a simulation of boxes bouncing within boxes within boxes.  Essentially, I need a hollow box - something that can properly simulate collisions from outside and within.  Since all the volume-bounding ODE objects are solid, I'm stuck.

My best thought is to somehow attach six faces from finite planes to a body.  I'm note sure if there's a more efficient way or if someone's figured out how to do this.

If I do use finite planes, I'm also concerned about objects passing through the plane and escaping (if the timestep is too small).  Seems that there might be a way to use the collision flags to define which objects are "external" or "internal" to a containing box.  

Alternatively, is there a simple way to modify ODE to permit hollow objects?

Thanks,
m1ke0