Anyway, as Junk mentioned, I was lucky enough to help him make some room in his garage and picked up his Hannibal roof tent.
I have it mounted using three sets of Yakima A1 towers with 78" load bars (kayaks/bikes etc. are mounted outboard of the tent). This should be more than enough to hold the static weight of two adults, and the dynamic (moving) load is well within Yakima specifications. The tent opens to the rear with the ladder extending down past the open rear hatch.