OK my plan for "Beefing Up" my mini-tub install.
Like I said before, (on the convertibles) GM addressed the loss of rigidity that the roof gives the coupes in a few different ways. One of the major ways it did this was to build in more support between the wheelhouses with a much larger and more structural brace between them (the rear seat brace.)
Here you can see where they used some 20 gauge sheet metal to mount the seat brace to the wheelhouses. (NOTE: this brace is not clamped tight up against the front of the floor... so it is sitting almost an inch forward and low.)
