Another thought I just had is belt width..people have complained from the start about the harsh engagement of the viper and a huge factor in that is the belt to sheave clearance. When comparing a Yamaha belt to a gates belt, the yammi belts are narrower, not a huge amount but it is noticeable. So with a narrower belt when your weights overcome the spring pressure and engage the belt it’s not a smooth transition with the narrow belts because the larger gap between the belt and sheaves makes the clutch “slam” into the belt so to speak. Now different springs and weight profiles can alter this and improve it..but the issue still exists. The 911 cover that you can adjust that clearance would be a great option. I don’t have one nor have I ever used one, but the concept and idea is great..another great idea is simply a wider belt. If you’re into taking comparison measurements, try some different belts and and with a feeler gauge check the clearance on the primary clutch between the belt and sheaves. On mine with the gates belt and .018 gauge fits and a .020 gauge does not, that’s right in the desired range. Even with yamaha’s Stiffest primary spring with my weights and roller setup my engagement is 2300 and very smooth..but the kicker is that when it engages the sled instantly starts to move, no belt slack to overcome and no belt slipping with the gates.