...hold on..
The more weights you put in, the lower the engagement RP becomes. Remember, it's a centrifugal clutch...as it spins round the pucks want to slide out and push the halves together because of the taper slide they are on. More weight means it doesn't have to spin as fast for the pucks to overcome the spring force and push the halves together....less weigths and you need more centrifugal force to overcome the spring force = higher rpm.
Top speed. If you put too few weights in you may, as Dean experienced, hit the rev-limiter before topping out on the clutch movement..hence clutch tuning, what are you aiming for. I don't think I would go below 7 or 8 weights myself....doesn't matter what's done to the engine, it's going to slam into motion and be very jerky on take-offs....the more weights you have in the smoother your take-off is, it's easier for trail riding this way, you're not breaking traction, with every blip of the throttle.
Best case is (IMO) to have as many weights in as allows you to take off with the amount of pull as desired, build torque into your engine to allow it to pull hard on bottom end.