Do not use ANY foam. Even closed cell will allow water to wick between the tank and the foam. I used closed dell foam on a tank in another boat and it corroded where the foam was BAD. Remember it's ok if water gets on the tank. It just has to have a way for air to get to it so it will be able to dry out. So anything that holds water trapped against the tank will cause crevice corrosion. The vinyl tubes I used under my straps is slit open lengthwise to allow any water that get in the tube with the strap to get out. There is no perfect tank install since there has to be some trade offs.. Do you really need your tank to last 30 years?
