If your system is going to low with six adults, it is not functioning properly. I have had far in excess of that in mine. I put tons of bricks for a retaining wall in mine. It had to be a couple thousand pounds (yeah that was dumb.) As soon sa I closed the door, the car moved to its proper position (which impressed the Home Depot guy, who said "I hope you are not going far, because you are going to bottom out all the way home")
I wonder if it has to do with the fluid level?
on another note, my local lexus mechanics, who are terrible, once did something with the suspension, and while on a trip, a pressure valve or sensor came undone. The fluid leaked, and obviously, the car went immediately into the low position. The Mechanics in Boston knew reight away what it was and called my "home team" mechanics a bunch of idiots.
I think if you live in a city outside the coasts, fewer people have these, and the guys are not trained on the 4wd and the suspension.