Yours may be different, but we used two layers of 3/4" insulation and 3/8" rubber matting. The matting is a bit heavy, but it won't go anywhere! Boat has been sitting out in the weather and is holding up great.
By the way, don't put that foam stuff where the gas tank is. I think styrofoam and gas mixing makes something that could ruin your day with one spark.
Edited by Jacob645 (11/24/14 02:22 PM)