i have gotton better 60' by reving it high and sliping the clutch as fast as i can with keeping the front down, dont pop it or youll go up
finding the right rpm launch is also important i found that i launch the best around 8-9K
if i could ust get the clutch out faster it would cut my 60's down even more
so i basically pull up shift gently into first rev and hold to about 8.5K hit the yellow light and let the clutch out as fast as i can, let off the throttle just a hair for my 1-2 shift, then pull her back and dont let go of the thottle for the other shifts.
i still need improvement cause my 60's are only low 1.9s instead of the 2.0's when i first started.