Surprised that your limited by so much.
Thus you must spend a lot of time with the aux and tip tanks empty. Does this cause a problem with the bladder in the aux tanks drying out?
On the contrary, I very rarely put 4 people in the aeroplane.
Have you had your aircraft weighed recently?
Much more often and recently than most aircraft, I think. 2610 lb. I obviously can't speak for the aircraft you fly/flew, but I get the impression that a lot of owners/operators do a lot to avoid having their aircraft reweighed for fear of bad news.