The structural integrity can be maintained if you replace one piece of tub at a time. Screwing a board between the tailgate opening is helpful. I have seen people install a brace above�and toward the front of the wheel houses too. You may consider more bracing if you plan to do the cargo floor.
I started by replacing damaged pieces on the sides. Once complete here, I flipped the tub on edge and replaced one portion of the floor at a time.


I did re-install the tub a few times to make sure I was keeping everything in alignment.
There are clearly other ways to do this. With limited space and skill set, this did work well for me.
Hawk