I went from 1.6s to 1.4s using the info in this thread. I was using 2.68 and tried everything i could to slow the arms down and couldn't get it done. Now I am using 2.86 and i think its alot easier to tune than 2.68 by far. I went from a 2.23 with 2.68 prim to 2.11 with the 2.86 and pulled that gear easy by tuning the clutch.
Track time/seat and your time slips will tell you what direction you're going.