There is a difference between slipping a clutch and mechanically controlling how fast the disc/input/driveshaft get to crankspeed. Sometimes you need to stop buying parts and spend some time learning.
Glad you brought that up, there is a difference. If you are shifting WOT using the clutch, a SoftLoc style clutch actually has pretty harsh initial engagement characteristics due to it's centrifugal component. Basically at the shift point, centrifugal assist is at it's maximum. As a result, excessive clutch pressure actually pulls engine rpm down sharply after the shift, until the centrifugal relaxes enough for effective slipping to occur. That sharp drop in rpm just after the shift is not ideal, as it indicates a concentrated spike in torque delivered to the input shaft. That centrifugal assist is also the reason you have to start at a lower rpm and "drive into the clutch" when launching a properly adjusted SoftLoc style clutch...if you launched at a higher rpm, you would not get the desired amount of initial slip.
Simple controlled slipping (no centrifugal component) combined with sufficient clutch pressure, can effectively spread rpm loss after the shift much more evenly over the same period of time. Also allows launching at a higher rpm without adding inertia energy from the rotating assy. Both of those characteristics can make you quicker if you take advantage of them.
Ditching centrifugal assist and switching to a damped diaphragm PP can also significantly reduce clutch maintenance.
