You need to double clutch when upshifting too. You only do this with a lightened flywheel, because the revs drop much faster so you have to pop the revs back up to where they need to be. So to double clutch you release the gas and push in the clutch like normal, but you then re-engage the clutch and blip the throttle to get the revs where you need them, then push the clutch in again and re-engage like normal, now if you get a better clutch and a 50% short shifter, you can probably keep your revs in a good range with a lightened flywheel, hope that helped.