I was on a thread about this a while ago, the issue was the weight. 4 adults could weigh anywhere from 400-800 lbs. With our 2 teenagers the total weight would be 550lbs and that was considered too much weight on the roof by someone else on the thread.
So in my case my Bajarack can hold 600lbs static, the weight of the tent and 4 of us is too much, so depends on what your tent sits on and weight of adults.