Reviving an old thread... I'm hoping to begin this project myself. It's been a few years, have you tweaked the design at all, noticed any further weak points, scrapped it and started over? I'm interested to hear your long-term results of this and what, if anything, you'd change in the re-design.
The design looks great - my welds are probably not even as pretty as yours, plus I use a small flux welder, so I can only work with 1/4" material, and I have to "double-up" the metal in points that I want to add strength.
Thanks!