Will this work? Purchased an Englander 30 for my daughter. Manual says R value of 1.5. So if I construct a pad 48" x 48" x 2" as follows - 3/4" frame - 3/4" strips every 12" on center, 3/4" polyisociante insulation in between strips, 1/2" plywood on top, 1/2" Durock on top of plywood With 1/4" ceramic tile as finished floor. Floor under this pad is hardwood with carpet on it. Will be removing the carpet under the pad. Any suggestions or corrections greatly appreciated.