Interesting approach to getting a smaller gap and I can see how the panel could be screwed in place rather than tack welded for the same end result.
I have the driver's side panels screwed in place and fit checked the door. With the belt line matched the door gaps are pretty consistant but perhaps a little tight on the lower half of the rear. However, the door does not close without pressure from the outside. It appears that the hinges (or at least one of them) needs to flex the hinge post to close the door the last 3 or so inches. The hinges seem tight with the bolts installed but there could be a slight gap against the hinge pillar (not sure what is keeping them from being tight). Given that the top half or more of the hinge pillar has always been attached I assume the problem is that the bottom has twisted affecting the lower hinge. However, the upper hinge is very difficult to get into the pocket due to the torsion spring that serves to hold the door in the open position and so the opening is beat up so that may be part of the probelm as well. Prior to any work the driver's door was more difficult to close tight to the latch post so the problem may stem from it's previous life. One concern is that if I flex the lower portion of the hinge post to address the door closing issue the lower hinge will move rearward making the lower rear door gap even tighter than it already is as the inside edge of the hinge pillar is fixed by the rocker panel and seems pretty solid. I clearly need to do more investigation to detemrine what needs to be tweaked but as I learned on the passenger side door, it is critical to get the door fit correct before welding everything in place.