I went through this high preload problem with my YZ SSS forks when the RaceTech springs were too long. I was told by several people in the suspension industry that I should not cut the stock spring perches more than 5mm (to reduce the preload) because that can apply lateral force on and potentially pinch the inner chamber fork tube which can dent or bend the tube causing restriction.
While I purchased the race perches that I was able to cut to lower the preload more than 5mm, it would have been easier to buy the correct KYB springs that come with the correct length for 5mm of preload.
https://www.suspensiondirect.com/shop/sdetcv24-set I also needed to open up the windows to match the stock windows.
You can get parts from
https://www.suspensiondirect.com/shop/ or
http://www.technical-touch.com/
Based upon my spring length problem with RaceTech I will be avoiding them in the future.