Too close this out in case someone else searches and wants to see the followup, here is the pic after riveting the unfinished, loose aluminum sections together as suggested.
For others who plan to do the same thing, what I had to do was:
1. Drill from inside the cabinet outwards since my ProPride hitch leveling jacks preclude opening the door fully.
2. Rivet the same direction.
Caution: locate the hole for the rivet down far enough for the seal when replaced to sit above the rivet. Had to replace one before I considered this...