Nice setup, but I actually have the flip seat bracket, although from Clavey, but it is the same. I have learned from my mistakes and the bracket is on the front bar. flipping the seat forward to access the box will not be a problem space wise, its not even a problem in my little super duper compared to your battle ship. But of course if you want the PITA of swapping in the field, I guess you can only lead a horse to water
On another note, be sure to put a foam pad in the bottom of your drop bag or else that plastic/can combo will probably wear a hole in it in nothing flat. I actually have glued a foam pad (just the cheap blue kind from Wallyworld) on the bottom of all my ammo cans for putting them in drop bags and also strapping to a frame, helps with them not sliding when strapped to a frame directly. Then you don't have a chunk of foam floating around that gets lost.