Hello.
Trying to setup something simple, but no joy.
Just as a test:

Two poly cubes, one above the other.
The one above is thinner than the one below.
Nurbs floor plane.
Select both cubes and set gravity field and set nurbs floor as passive body,
Cubes drop and lay on each other and the floor, as expected.

If I set up the same as above but before I inroduce gravity, I select the top cube and delete the bottom face and then continue as before.

When the cubes drop, now the top one drops through the bottom cube and rests on the floor.

Why won't the top cube merely rest on the bottom cube, on it's topmost face, instead of just falling through the bottom cube geometry.

Maybe not possible?

Thanks for your time.