I have an ARE Z cap with a Con-Ferr 4'x5'x6” roof rack and it can take the weight up to about 400 lbs easy, maybe more. I have had a canoe, two MNT bikes and gear up there that was well over 250 and I cruising at 70-75 MPH for 600 miles at a time. When I load the canoe and bikes, I am up there to, making it 420 lbs. On this cap I mounted through the honeycomb center and it worked out ok. I have 6 mounting spots and 12 holes (1/4 20 bolts) that are reinforced with (6) 3”x 6” pieces of aluminum on the outside and washers in the inside. I think it works better when you mount to the curve of the cap. That's the way it was on my last truck and it felt stronger and had no aluminum plates.
In December I had the roof top tent on the cap and with me and 2 of my younger daughters up there, it was fine. About 240 in people PLUS the weight of the tent and rack. That's all the testing I have done with the tent so far.
For the last 4 years I have had my 35" spare up there on a 16x10 rim and its not light!!
Louie
PS.....Carl, I need some tips on OBX!!! I am planning a trip there from June 7-17. Planning on driving from southern tip of the Core Banks to carova...plus the boat trips.