Bars for Roof Top Tent

I usually look at this forum regularly but seldom do I reply. Anyway as no one else has I thought I would help you out.
The loading of the racks is probably not the issue but the loading of the gutters may be. From memory they are rated at 100kg. Whether that is per gutter or in total is anyones guess (might state in the vehicle manual). As you stated, this is a static weight and not a dynamic weight which means 100kg on the roof when you are parked. Depending on the shape of the load, at speed it may increase or decrease downwards force.
Personally, I installed 3 factory toyota roof racks to spread the weight out just a bit more then the standard 2 bars and had no dramas. I think the bars were rated around the 100-120kg mark. When you start looking at the racks I found they fitted into 3 categories. Very light, standard and heavy duty. The heavy duty ones are made from gal plate and are typically used by tradies and I wouldn't trust the light ones with my surfboard.
Hope that helps.
Tim

Holden4th,
I've always used four racks for the rooftop tent, just because it felt a better spread and seemed solid when two of us moved around in the tent. I have Rhino Sportz racks rated at 90kgs each.
regards
Garth