The steel roof structure that holds the torsion bars is glued to the top of the fiberglass. This is prone to separating over time, and distorting due to the forces of the torsion bars. After removing the “rear screen upper finisher” you can see the steel roof structure covering the fiberglass above the rear window:
There are a few ways to secure this, and I chose a simple method. I secured the roof structure to the fiberglass on the back of the car, above the rear window with some stainless sheet metal screws.
I also covered the screws in RTV sealant, before screwing them in, to keep water out. That’s probably overkill, but it was on hand and took a minute.
(4) Stainless Sheet Metal Screws: $2.80 @ Ace Hardware