Since the last set of posts, I put the passenger side door back on, just to make sure that side still looks OK. Thankfully, it does. Also per the suggestions you guys had, I inspected the roof overhang and measured to window-frame-to-targa-bar. The roof overhang was even across the back. I took the targa off and the frame to bar was dead on 25-1/8" on the passenger side, but about 25-1/2" on the driver's side. Which of course matches the twisted door gaps on that side.
I checked the cockpit for square by running strings diagonally across. The string just touch in the center, so wherever this problem starts, it is behind the firewall.
Click to view attachmentSo I spent a couple sessions just sitting on the couch with a glass of bourbon and pondering the overall structure. I think the problem starts with the joint I made between the horizontal section of the long and the angled section. Right where the arrow is below, you can see a strip of metal about an inch wide that joins the two.
And here is what killed me... My dolly is on the short side - it goes from the front axle to the engine mounts. So the whole back section is cantilevered. I was counting on the door braces to hold everything in place, but they acted like the wishbones on a double wishbone suspension. Like the parallelogram that
@Superhawk996 mentioned, all the linear measurements are held, but the angles can change. So when I measured the door opening at the bottom, it was correct, but it was no longer dead horizontal.
Click to view attachmentSo I put that circle right about where I think the whole thing rotated. To fix this, I need to cut the long at the arrow and open that gap up about a centimeter. I'll need the brace to pull back at the shoulder belt point to straighten it all up, then re-weld. As suggested, I'll whip up a brace that can go on with the door in place.
The engine mount will have to come off... I won't use it to try to pull anything into place, but it will have to be repositioned because the whole rear is going to move and it needs to stay where it is relative to the rest of the car.
Right now the only thing that bothers me about fixing this is the inner layer. Here's the reverse angle below. That sleeve was made so that no welds on the outer would coincide with welds on the inner. They aren't even in the same direction, all the outer welds are vertical and all the inner welds are horizontal. It's going to be tough to cut through the long and then put it back together without the outer and inner both having a weld in the same place, right on top of each other. That inner layer is rosette welded solid in there. It's going to be tough to remove any part of it to get the welds where I want them...
Click to view attachment