I can do 2" of insulation on the floor cause I'm only 5.9. Does it matter if the rigid foam is under a plywood subfloor, or on top of it? what is our goal, to keep heat and cold from coming up through the floor or escaping down through the floor. I know I want at least 1/2" of rigid under my floor to house the PEX hydronic system. Would 1" rigid with 1/2" plywood and then another 1" rigid be a good solution? That way I'm only going through 1" of foam to secure any cabinetry.