[eksjay]

I have a Pioneer Rhino Rack bolted across 2 (Rhino) gutter mounted bars.

It is as solid as a rock. Three gutter mounted cross bars should be sufficient.

Maybe if you get a Pioneer rack, you could use it for other things when the tent isn't up there. It adds utility to the car as you could carry an assortment of things that can't easily fit inside or you wouldn't want to have inside e.g. Jerry Cans, long ladders, large flat packed stuff from Bunnings/Ikea etc.

Before I got the Rhino, I used to put heavy loads on the factory bars and when I look back at it now, I don't know how I got away with it. I used to tie the cargo down also using the roof rail holes.

I agree about things becoming unstable if you pack too much weight up there. It can become a sailing boat.