Thinking a little more about outfitting...
For extra storage, a PA-60 60mm mortar can/AN/RVS-14 monocular night vision device case is a perfect height to fit on the side under the angle of the tub.
The front wall of the chuck wagon might be a good place to mount my sand ladders.
Although they're not often needed (hopefully never!), and they weigh a bit, so perhaps they'd be better mounted under the frame. The ones I have are 48" long, so they would stick out a few inches on each side of the 40-ish wide frame though. Sticking out they could be an opportunity for cutting shins, so perhaps mounting them at an angle under the tongue angle rails would be better.