When I ran the 2013 East Coast Mugen Challenge, back in August I was running the "rcgod" setup and running 7/7/4 for diffs and 2.9 rear spring rate.
Lookup the 2013 East coast Mugen Challenge race on Youtube or "snwchris" and you'll see a video of the track. By late saturday and into sunday the track was getting rough and loose, but the tekno handled sweet.