Nice bike! and a big thumbs up for the Geigerrig !
As far as sag- most success has been found with pre load on the CORRECT rate spring in the 10-12mm range and let the sag fall where it will. I believe the stock spring is 5.2 and is ok for up to about 180 lbs ungeared rider. look here for a ton of info from the gurus here
http://www.gasgasrider.org/forum/showthread.php?t=1628