It was glossed over in this thread but this Stage6 clutch is the cat's meow so I will revive this post. I need to get the red springs but it makes a huge difference on take-off. I've got it engaging at 5000 or so rpms and with the red springs (where did the GY6 engage - maybe 2500rpms?), I should be able to get it well above 6000. I guess I should mention that you can change and adjust the springs without taking the clutch off the bike and if you get their clutch bell, you can do it without taking off the clutch bell.
Of course, it adds another variable to trans tuning. The more I preload the springs, the more it moves around my rpms/speed. I was hitting 42 mph at 7700 rpm and now I hit 37 at 7700 rpm. (edited)