Mine is a Cascadia Vehicle Tents Mt. Rainier, 72″x48″ stowed, 72″x96″ mattress, plus covered ladder area. Ample space for two of us. Need to add a trailer for more than two.
160lbs, winch-hoisted and stored (but on top of the Ascent pretty much year-round). Old style Thule load bars and feet. The Ascent barely notices the weight; I don’t sense any extra leaning, but I imagine there is some if turning aggressively. Highway gas mileage does get nailed however.
I have not tried the zip-on annex, as it kind of violates my personal purpose for a roof top tent (nothing touching the ground, no hosing off the floor mat of scorpions). But it would add some space, maybe for an extra cot under the ladder.
F.S.