I already glued 1 layer of the Reflectix on my boat (a work in progress), including inside the storage areas/cabinets etc., intending to get new Vinyl fabric to cover it but after seeing the "strip plank" type installation noted above I'm now going to finish it that way.
The Reflectix has been doing a great job w/ just 1 layer (R 5?) and I'm only using "1" 20 lb. propane tank every 7-10 days and keep my boat 72-74 avg. inside w/ winter lows that avg about 15F here in Rhode Island.
On the bottom of settee's storage area, I used 1/2" foam carpet pad and it also made a difference but I may change that out w/ some closed cell.
This is a mailorder closed cell foam page, but they sell all types of foam, including custom cut (V-Berths etc.), really reasonable. Poke around, they have lots of deals.
closed-cell foam, slow recovery memory foam, qualex foam, polyethylene, neoprene, polystyrene, EPS,