Ok, update after 2 months. Sorry, at least there are pics. Have been camping 3 times in new trailer already.
This is what the 4th door opening looked like.
This is what it looks like now.
I fully welded the new hinge setup. No flex at all.
The lower hinge is notched into the floor for clearance.
The inside view shows how I sectioned and boxed hinges from a 1966 F**d. There is something good from F**d.
I connected the hinges to the roof with a section of 2x2 steel tubing. I can't take credit for this idea. Frizzle Fry did this on his tahoe. Makes the side very ridgid.
Also connected the back of the B pillar to the floor. B pillar is not done but doesn't move anymore.
Then painted with POR 15.