Not bad..welds look good. The only thing that you might have wanted to consider is pan ends. This will give greater strength for the welding, rather than just a straight but as you have done, and make a hell of a strong tank. We build a lot of fuel cells at my work, and supply a bunch of mfg's parts as well, like Gen-Rite 4x4. Baffles are important, the easiest is to just clip the corners.
