Fuel Tanks

[Basketcase]

Hey guys. I just aquired the stripped out hull of a 20' center console. All I have is a hull and stringers. First on the agenda is to put a transom in there but I figure the second step is to figure out what I'm doing about a fuel tank as that will determine the structure of my floor setup. I was thinking of one tank about 70 gallons or so. I talked to the guy that I usually use for this stuff. He is an amazing fabricator and making a tank like this is like asking the Paul senior to make me a moped. His original thought was to make the tank with .25" aluminum. Right off the bat I thought that seemed aggressive but he said hes seen lesser tanks crack. He said with that thickness and a few baffles that it would last forever. I assume there are prefab tanks I could use. He asked if I could find some specs as far as thickness etc. I'd like to use him to build me a tank (unless it's twice the cost) because he can make it exactly how I want it and hes a good friend as well. So I suppose my question is, what are the specs of a tank this size? I figured if it was properly bedded in some foam and properly attached that .25" aluminum may be a bit overkill. Any input? Thanks everyone. Looking forward to getting this boat moving.