Well, I couldn't leave the back door 90% done, so tonight I installed the rear power coupler frame piece.
Unlike the back door panels, I'm using silicone to secure the frame piece. This is to allow for easier removal should I need to repaint the blue corners in the future. While I might want to repaint the white panels too one day, I used JB Weld for the panels rather than silicone because JB Weld won't harm potential autographs in the future, whereas silicone wreaks havoc with them over time. The odds are pretty slim that the back door of droid #2 will ever be autographed, but better safe than sorry.
I scraped the area with a razor blade where the frame for the rear power coupler will rest against the inside of the back door. I also scraped the front top and bottom curved area of the frame piece. This removes oxidation and roughs-up the surfaces so the silicone will get a better grab on the aluminum.
I then cleaned the pieces with acetone. Next, I ran a thin bead of silicone on the curved parts of the frame piece.
I then carefully set the frame in place on the inside of the back door, and ran silicone all around it.
I ensured that the piece looks as centered as possible from the front side.
Hopefully this will cure in 24 hours, but we shall see. I have a history of mixed results with silicone.