I read on several forums, that while sitting on the bike, the the suspension compression (springs / shocks) should be about 1/3 of the total travel from the relaxed position. This sounded logical to me, and it seems to work out. The fronts were only about 3/4" on compression. One of our other members, shortened the spacer in the front fork tube, to soften the front end. I did the same by cutting off about 3/8". You can also add washers in the tubes to stiffin it up as well. This acts the same as the preloads on the rear, which the fronts do not have.
Then I replaced the 10W oil with 15W, to increase the dampening effect. One member even found there was a shortage of oil from the recomended specs.
The softer front did reduce, quite a bit, the sudden shock & jolt when hitting bumps and heaved pavement.
The heaver fork oil slowed down the reaction to it.
The front carries the same load, riding solo or 2-up because the passinger sits directly above the axle. But the rears need the be adjusted, depending weather you are riding solo, or 2-up.
Speed is also an issue. typically, the faster you go, the stiffer the suspension should be. A rear setting of 2-3 might be fine @ 45 mph, but at 65-70 too soft, and should be set up a notch. Most wobbling at high speed is caused by
1-too soft a rear setting
2-low tire pressure
3-loose mechanical componets, (steering head, axle, etc)
Many of the aftermarket shocks for the rear have adjustable dampers for the rear, which acts simular to changing the front fork oil weight.
Hope this helps