Jim,
there was a layer of thin foam (perhaps 5 mm thick) under the MB-Tex on my 230SL but most of it was crumbled except in places where there had been enough glue to keep it there.
When I changed to leather I put a layer of high-temp polyurethane foam underneath again because it helped to get the leather to look smoother around the curves.
Alfred
1966 blue 230SL automatic