[techie610]

Sounds like its doing pretty good as is. But I would probably got to 14s and test it.
Sliders are much better than rollers, and react a bit differently. Get some 14 sliders, run it for a few miles. Pay attention to the ACCL and RPMs. Also, take into account the reaction time when letting on and off the gas.

When I went to sliders for the first time, riding at .25 throttle and then imeadiately going to WOT, the ACCL and was impressive.

On a side note: I wouldnt use a rubber belt. Kevlar runs and reacts much better and faster.