Originally Posted by Sundancekid
What is the design flaw with the black cap.
What kind of bracing should be added?
Below the floor, the frame does not extend into the rear cap to support it. The cap is 'hanging' on the roof and screwed to the sides walls.
The bottom of the cap shifts around from side to side, you can see it your mirror driving over the right surface. If all the rear panels moved in tandem it would be ok, but they don't, So screws pop out, panels separate from the cap, sometimes the panels stay partially attached and rip. There is also some structure just above the trim line that will push outward from the inside of the cap.
The cap shifts side to side. Sometimes you can see a slight bulge from whatever is pushing from the inside. A side benefit to this is the object is pushing just enough to cause the clear coat and/or paint to craze.