cliping the polies may be pretty slow. A further solution coul d be:
render the solid material as a simple quad or cube that covers the screen, with the correct distance to the camera,(maybe use a 2nd camera for this, far from the world center) then render the scene with the "holes" produced by things that are clipped using a CameraClsMode that will not erase the background. Now the solid material should be visible in the holes, with dynamic scaling etc so textures look right.
render the solid material as a simple quad or cube that covers the screen, with the correct distance to the camera,(maybe use a 2nd camera for this, far from the world center) then render the scene with the "holes" produced by things that are clipped using a CameraClsMode that will not erase the background. Now the solid material should be visible in the holes, with dynamic scaling etc so textures look right.