The bottom of the yoke to where? I measure sag with a cable tie on the stanchion, measuring the difference between the forks fully extended, to when the bike is sitting upright, with about 10 litres of fuel. Mine is 17mm, but anything from around 14mm-27mm is ok I believe.

You can then set the bike up to sag an amount with the rider on board. Do you mean 3.5 inches of travel with you on board?
_________________
NSR300R - Why did i ever have a 250...