Actually the tank that Hume is fabrication is aluminum but note how he has radiused the edges of the end plates, this make the weld joint a butt weld not one where the two pieces of metal are at 90 degrees and a sharp edged corner, which makes a really ugly weld unless you happen to be making the tank from 1/8 or thicker material. Also this makes a much stronger corner joint. I know that this is pretty much standard practice for guys like Hume but it should be a good lesson for anyone trying to make a tank for the first time. An additional plus is that the tank will be just another of the hundreds of exceptionally "neat" piece that have been built for this project.
Rex