I have a flat roof, the contractor wants to use 1.5" polyiso foamboard over the bare wood deck, I know the benefit of added insulation. But since the foamboard compresses when walked on, wont this ruin the roofing early in its lfe cycle since as the rubber roof ages and hardens, walking on it will likely ruin and crack it as the foamboard compresses? What is the best way to do this. He wants to use US ply Duraweld APP polyester reinforced roofing. Is this the best roll roofing you can get?