The right way to use spacer in bed to raise camper?

I had the same issue with my Lance 815 when I upgraded from a 2004 to 2015 Ram. I built an interlocking frame of 1x6 and filled the void with 3/4" foam. Plenty of clearance and a much warmer floor. To keep it from sliding around on the wood, I lined the 1x6 with a strip of anti-slip shelf liner. Haven't moved yet.

I like the full support the horse mat stall but didn't want the weight.