The very hardest weld I have had to deal with was the inside bottom of an AD door. There is no structural support even close and it's about 3 feet across (guessing). Since you know this is going to be an accident waiting for a place to happen, really think about what is coming. You know it will shrink, you know if you are not real careful with the welding AND grinding, it will warp. No access whatsoever to the back side. I used butt weld clamps with enough gap to allow for expected shrinkage. I reasoned I would have about 1/16th of shrinkage, so allowed for 3/32. Tack in the middle once its clamped perfectly and frequently. Move to the edges by tacking every inch or so. Then no surprises at the end.
I learned the hard way and I listen carefully to Robert because he is a real professional. My first shot at doing that door job wasnt pretty. Now I can do any of this with confidence. Now if my painting skills were the same... There is just no substitute for practice.
