I’m building my own box. 2x3 steel for the main frame with 16ga studs. I’ll sheet probably with frp or aluminum. Rear tire carrier with storage too. I thought I didn’t want to tow, but just realized not every trip is an off road adventure. Lots of local trips I’d like to take a dirt bike or sxs along. So had to modify the design to keep some sort of towing capability involved. The ability to tow a lot and rescue from the rear hitch is a big plus in these trucks for me.