I used PVC, it was recommended to me by an old salt at the marina who also works as the boatwright at the Mount Vernon Estate. He has used it in several boats of his with success, mostly in the bilge because it's waterproof. He said to just go over to Home Depot and get a length of the 3/4" trim board and cut lengths out of it and screw them down and then bolt the fuel tank to them. I checked the specs for both the stiffness and melting point and am satisfied that it will be good for a long time, but will check it periodically to make sure. Hope this helps.