Had a very interesting chat to the guy from Harrop Engineering on the weekend regarding their superchargers, and he said that one guy with a 6.5 setup his bypass valve to a solenoid for better mileage at cruise.
Looked through you pics Phil, and I can't see any bypass valve. The valve works with vacuum on petrol engines.
Did you notice one? Should be towards the rear of supercharger.
I did mention about your belt issues, he thinks it's an alignment problem.