Glad I saw this thread, I was actually headed out to the garage to replace the fork seals, springs, fluid etc.   Like Deros, I used the racetech calculator and it spit out .857's as well.  For those running these springs, what kind of preload and fork oil amount did you guys go with?  It sounds like 120-100mm, somewhere in that area?

I don't remember the exact length I used for preload. I do remember the sheet had some sort of formula for setting preload. I followed those and rider sag is around 20mm, static is about 5mm.

For the oil height, I set an aluminum tube attached to some vinyl tubing down to 100mm. I poured in enough oil to almost make it to the top, gave the leg a few pumps to release air bubbles, and sucked out the extra oil through the tube.

Stanfield, once installed, your forks act like a sealed unit, and the volume of air in the fork acts like a secondary spring - as the forks compress, the air is also compressed. The air wants to expand back to atmospheric pressure, and thus resists compression, especially at the extreme end of the fork's travel.

I'd recommend you start at 120mm. Throw a zip-tie around a fork leg and take the bike riding. Afterwords, throw the bike up on a center stand, and measure how much of your suspension travel you're using. If you aren't using all the travel, leave the oil level alone. If you are, you can raise the oil level up.

The stock oil level is 99mm, but that's with stock springs, which are much thinner, and much shorter than the aftermarket parts. At 99mm, the air in the forks is being compressed into a very small volume (~20ml or less) with the forks bottomed out. The higher your oil level, the more stress you put on your fork seals, and the more likely you are to blow them out.

FYI: The GS500 has 103mm of suspension travel. I generally measure from the edge of the dust seal to the bottom of the zip-tie I keep wrapped around the fork leg.

For preload, cut your spacers so that they match stock (25mm. In my case, 1mm of pre-load spacer was visible above the fork tube with the forks fully extended.)

Then, assemble the bike, and measure your static sag, and rider sag. If they are within range, you're fine. If not, add or subtract preload to get the sag in range. In another thread, I post comprehensive instructions on how to measure pre-load.