Flatbed equipment choices....

That's a sharp Star. It would be tight to fit a steel tarp in a 24"x24"x24" box, but I think it could be done. Just gotta make sure and roll it up tight.

Couple ideas. It doesn't look like there is much room, but can you loosen the tank straps and slide the fuel tanks forward closer to the exhaust so there's only about an 1' of space between them? Then I think you could re-mount your quarter fenders about 4" closer to the tires without causing any problems. That might be just enough to let you fit a 30"x24"x24" box. The extra 6" would make a world of difference.

Just thinking out-loud. Feel free to criticize.

 

Could put the batteries all on the other side or in their own box. This is the first truck I've seen with them split up like that. You could get a side box on by switching to one smaller tank but I hate anything that cuts fuel capacity. I have dual 159 gallon tanks on this truck and I love it.

I'd see what your revenue stream is going to be like running with these guys. For me things are only expensive when I can't afford them.

 

Move your 1/4 fenders back closer to your drives. Looks like you could gain a lot more room for boxes.

 

You put a step box on each side, a frame rail box ahead of the slider and a three door cabinet rack you will have more then enough space.

 

I buy from Tarpstop fairly often. They ship very quickly and have everything in stock. They can make custom sized tarps and ship them next day as they sew them up in their shop. Is the material made in the USA I doubt it. Its thin and light I usually get holes in mine from rideing around in the side box. But the prices are good the service is great.
My thoughts on the chains and binders is this skip the yellow quick binders they can be akward to use. The chains I would go with 3/8 and the standard Durabilt ratchet binder. I woud also steer clear of the snap binders. I go to places that will not load you if they see a snap binder on the truck even if your not using it.