I have heard people say they use foam insulation board under their camper as a riser with a bed mat on top. I have heard others say they use the insulation foam but no rubber liner and have no camper...
for 2 reasons, the first and main reason was for support of the water tank for use off-truck. This model was never designed to be use off-truck and I was told by S&S that it was very possible for the full water tank to rip the floor out of the bottom without more support so....
The second reason was to keep it from hitting the cab lights, it had divots in it when I got it from them, and it sat very close to them.