I would always have at least 20 psi in the shocks. The bike really handles poorly with no air in the shocks. Same deal with the damping, I keep mine at 3 lines regardless of whether I am 2 up or not.
Tire pressure is very important also. 35 psi is the minimum I would ever go. Kawis recommended 28 psi makes the bike handle like crap, especially if loaded up.
When I take the wife and all our gear on a trip, I make sure to put both tires and both shocks to 40 psi along with 4 lines of damping. If you are a heavier rider or you ride 2 up, you must try riding with that setting. Its almost like riding a whole new bike.
