Took out a section of the floor for being to soggy and just wondering what I can use for the bottom backing? What I removed was carpet, 3/4 sandwich board, some sort of insulation and the fiberglass as the outer most layer. The fiberglass just kinda seemed to sagged/be resting on the muffler (was burned threw) Also does this part of the floor offer structural integrity? Seems to only go under the benches about an inch on each side. Was thinking just replacing with same type of board, insulating the whole floor from inside the RV and laying carpet. As for the bottom thing just spraying some truckliner. Thoughts?