Hi Greg,
I have used thinner cans many times fo make tanks. Gallon dope cans, too. Strip the paint where it needs to be soldered, don't wire brush it or sand it very heavily since it will cause the "tin" to be removed and it willnot solder too good then.
Bill <><
Added: the can material is a *little* bit heavier than "bought" tin, but it isn't that noticable.