Why Not?
Tell me this: Why WOULDN'T you put twin Cats on?
You could do it like that. In japan there was a nice dual system that was set up like that, with a tip exiting each side of the car at the rear. Four tubes out back, like resonated chrome muffler tips. The system used two 50 or 60MM tubes off the collector flange. It had pre-muffler/cat up front depending on how you ordered it, and the split collector/resonated tips out back. Distinctive sound. The twin pipes ran alongside each other in the tranny tunnel, and split branching off right/left near the diff-rear cradle assembly.