Early A Trunk Quarter Panel "Abyss"

I'm looking to do something similar to one of my cars too. I remember seeing them on an early B or C body. They weren't a sponge or anything solid, it was more like a heavy cardboard panel over a couple of brackets that went down into the crack. I'm thinking of making a couple of pieces of styrofoam stands shaped to fit the quarter panel and glue them to a flat fiberboard panel that would fit even with the top of the trunk floor. Then a carpet pad over the top of everything. I wouldn't want anything absorbent down in the quarter panel.