Okay so I've completed the 'fix' of this glorious accident.
Here is a picture of the area in question after the pop rivets had been put in:
You can see the hulking cherry max rivets holding the lower drag fitting in place with the 2 rows of pop rivets on either side.
Now... it was suggested that I use Cherrymax rivets on these locations. I bought a variety of pop rivets to try and fabricated a test setup of ~.114" (the approximate thickness of the pieces being riveted together) to see which one would work. The biggest problem was the space between the main fuselage skin doubler and the bulkhead. Unfortunately cherrymax rivets were too long. Other rivets were short enough, but lacked the grip length. In the end what wound up working best were cherry MSP-42 rivets.
The MSP-42 rivets were also SLIGHTLY too long... just short of 1/8". BUT... once you started to slightly pull these rivets they quickly shortened and allowed the rivet to push easily flush. Only the MSP model was just the right length that you could pull it somewhat, push the rivet in flush, and then on the subsequent pulling it'd tighten up strong and set correctly.
Now you might be saying, 'but those aren't countersunk rivets' and you'd be right. BSPQ-42 is the countersunk version of the same rivet. The problem is that when settled into the hole, the BSPQ rivet was far too long. Even when you started to pull them in an attempt to settle them in like the MSP rivets they'd tighten up in the hole too much before they'd be short enough to push them in the rest of the way.
In the end the rivets set very well and there was no rotation after setting. They're tight, they seat all the pieces together very well... and hopefully won't start shattering apart in 20 years.
I hope this doesn't affect the resale value?!