that is a great set up....i got my inspiration for my camper shell build out from
@RoarinRow. i really like keeping things modular and easy to take out or put in. ypu mentioned a roof rack...i went with a yakima roof rack and a large cargo basket to keep extra totes and a place for a small LP bottle since i dont want it stored inside the closed off shell. the mounting hardware is 5/16", so there are 5/16" bolt threads sticking down inside the cap and in addition to using rings, i also went with 5/16" couple nuts that i threaded up on the bolts and then took a nice piece of oak board (1"x2") and drilled and bolted it to the coupler nut and now i have a nice wooden rail fastened to the inside of the cap to mount things to without having to try to fasten to the cap itself. versatility is my main goal when doing something...