Then I don't think I would need the foam since I will be bolting down the 2x4 wood frame of the tank to the 3/4 sheet for a complete pond armor/ low iron glass plywood tank build.Hangers are always a good option for anything that wont be handling the actual strain so I suggest them. I also suggest putting a piece of 3/4 plywood over the entire top and then 3/4" insulation foam board on top of that. It will help evenly distribute all the weight and if your tanks going to be acrylic it will allow the bottom panel to bow to take stress off the corners