What are your thoughts on round verses square fire boxes? I have found a couple of old smaller round propane tanks that went on a truck that are around 18 inches in diameter. Really cheap and to buy the steel to build the square would cost a lot more but I wouldn't mind if the square is a lot better. I know if I buy the steel I will probably get 1/4" not sure how thick the tanks are I'm guessing they would be close maybe 1/8 to 3/16's . I live in Mississippi so we don't get that cold even in the winter time so heat loss prob wont be a huge problem . This is going on my 80 Gal RF Build. Thoughts??