You could also decide to take a (controlled) leak or even drop a (perfectly calculated) load to adjust the sag on your bike, before going on the road.
There is always the possibility to finetune with adding weight by eating something or losing weight by wrapping yourself in plastic foil, go in the sauna and sweat it out till you have the perfect weight to ride the striple.
By no means , you use the preload before you have done the above mentioned actions.
I also used helium filled balloons tied to my helmet with succes.
Using the street triple on the moon on the other hand was no succes. Sag became way to low and I had to add an elephant as a pillion, but couldn't find a spacesuit to match the elephant or find an elephant that could hold his breath long enough in space.
A street triple is a machine that is very sensitive to the smallest changes
seriously. Of course you can adjust/finetune the sag by playing with the preload, but not infinite. If you have to adjust to far, it's not ok and another spring may be needed.
f.e. When riding with a pillion, it is normally adviced to adjust the preload, to get the sag into "normal" range
Don't some beemers have the ESA button to change preload and damping, according to weight, riding conditions or riding style?
Some good lecture :http://www.promecha.com.au/sag_preload.htm