your gap is set with you and all your gear on the sled on a flat surface.
on a viper you should have about 16-18mm of total gap. when the sled is correct it will all be on the top.
with the fra in the middle position
set the limiters loose to start, set on the sled, then lay over it and look at your gap
for the best handling you should have 50/50 spacing
if when you set on the sled the front end of the sled lifts and the gap ends up even then the center spring is too stiff,
if when you set on the sled the front end doesnt move up and the gap is too large on the top the spring in the rear is too tight
if when you set on the sled the front end doesnt move up and the gap is too large on the bottom the spring is too loose
dont adjust you hight with the fra, this is for adjusting the speed of the shock/spring through its travel
the optimal setting is to have the sled when you set on it have the most center spring preasure you can have without lifting the front of the sled with you getting on it and still have 3-4in of set in and keep the gaps even
also dont set your skid to not bottom out, if a sled bottoms out a few times durring the day it is fine, if it never does then your riding a stiff sled for no reason 99% of the time, if you bottom several or more times in a day increase either valving, and or spring preasure and fra rate to the fastest(bottom) setting
set the clickers in the middle on both settings and start from there