Beautiful work!
Quick question. Do you have to have a bar behind the front seats, the one going at about the headrest level? Would the cage be legal without it or if it was lower?
Yes you do. It could go lower, I put it where the side bars intersect the main hoop because I think it looks better. Also, it has to be at a level that would not inhibit the way a 5 pt harness would fit, and according to the book at no point above the shoulders.
...And, that is 1 5/8" .083 chromoly tubing.