Dave Osborn, I have read you square stern post several times, nice work.
My canoe has what I would call a transom rib that the transom is attached to so unlike the OldTown the canvas on mine attaches to the transom rib. So it goes around the corner attaches to the rib and the transom bolts on over it.
You state in your post "Once the stretch is done, tack or staple the canvas along the gunwales as you normally would." Did you continue forward to the bow or go to the center of the boat and tack forward and aft?