Tracrac mods - anyone added a second set of crossbars?

Have a Tracrac Trac One on my 12 Taco. Love the thing. Would love it even more if I could add another set of crossbars below the regular ones. Has anyone done that in a sturdy yet simple way? I'd like to avoid drilling holes, partially because tapping into the aluminum uprights and then attaching stuff with stainless hardware seems like a sure fire way to invite a bunch of corrosion (alu/steel galvanize quite aggressively in moist environments, and I live in coastal WA). Plus I'd like these to be easily removable if I need to put tall stuff in the bed.

Basically, I'd love to find or build some way to clamp a crossbar (like something from a standard roofrack) to the uprights and rely on friction from the clamp and the cant of the uprights to keep it up. Anyone done something like this?

 

Pics?