I for one would like to see the instructions for a foam bottom supported tank. I have not been able to find them in any search I have ever done. I have also definately not seen any tank instructions where the side glass sits on top of the bottom, the bottom was always inside. If it can be done I could build the tank I want the way I want and not have to deal with a floating bottom.
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I have built 5 that way including the first one I built, 40 years ago, and which I am still using. I also have 2 tanks from the 60s and one from the 70s built this way.
The styrofoam, will give where needed to take up differences in flatness, between the bottom of the tank and the support surface it is sitting on. As an example of how this works, I have some steel tubing stands I built. They carry 2 homemade, frameless, 48" x 12" x 12" tanks. When I first placed the tanks on the stands, the centre part of the tank was not being supported. I added 3/4" styro and when the tank was filled, the styro gave on the ends, untill the entire bottom was supported; the gap in the centre was about 3/16".
If the stand was out of level, the tank would still be out of level, but well supported.