Decided on how to modify the design a bit to compensate for cutting the top-aft door frame member too short (no overlap of the rear-bottom frame member).
After modeling in cardboard, cut the requisite piece and installed.
Then, fine-tuned the remaining parts and completed installing the stringer. Decided I didn't like the bend that occurs in the last two feet of the stringer due to a designed interference with a tube in the welded frame. So, I filed a corresponding feature in the stringer that allowed it to remain straight.