I just mounted a hardwood board on the wall in my coach. I used short "hollow wall screws" purchased from Lowes. The ones I purchased were rated for 1/8" thick walls. You drill a hole and insert the screw an tighten it up - four metal supports tighten on the inside of the wall as the screw is tightened. Once tightened, you remove the screw and use it to secure whatever you are mounting. There is a metal faceplate on the wall with the hole for the threaded screw so the mounting is supported front and back. I was amazed by how secure the mounting is. You should have no problem with these in foam and when you install it, the supports should have no problem displacing the foam on the inner surface. When you purchase them, they have the weight they will support marked on the packaging.
