I am having my 24 foot round pool installed next Friday and am torn whether to use foam on floor rather then sand. One, is 1 inch rigid foam ok to use? I can not find 1 1/2", only 2" and that is 34.00 a sheet. The 1 inch is 17.00. Two is tongue and groove better or square edge? My thoughts on foam is better insulation from the cold ground and smoother floor. Is this true? Thanks for any help asap please as I need to order my foam cove in before next Friday. Is wall foam worth the $$$?