The top out spring on the SP2 forks is about the longest of any bike out there, about 150mm. This really screws up accurate preload adjustments.
I had sent my forks to Kyle Racing and they installed a shorter top out spring (approx. 25-28mm).
The usual range for installed preload on forks is around 15mm, with a range of 10-20mm on average.
If a set of springs are shorted than previous, you can make a spacer to compensate for the difference in length.
Either thin wall steel tubing, or PVC is popular, depending on clearance of I.D. and O.D. of the cartridge you're using.
On some, I could use PVC, and on others I had to use steel tubing (which is harder to come by my area).
You want to sand the cut ends very smooth inside and out to prevent burrs from falling into the fork oil, which can clog up valves.