worked out that if Robs still got the 22" et at 9k he will have 10% slip at 90mph with the 8" of offset.
Thats a pritty "average" slip % for that setback possibly due to the small pitch prop and high prop revolutions.
meaning, if a prop slips .X inch every full rotation and Robs prop is a smaller pitch so needs more RPM to reach the same speed and as a result then slip will be higher.
no doupt Rob had the engine jacked right up too
Robs Propshaft at MAX RPM (9000) is 4812.83
Our Propshaft Rpm at MAX RPM(7500) is 4643.96
so in theory we should have very simular slip-
Rob having abit more setback to run the prop in cleaner water
And
prop slip per revolution X extra propshaft rpm so would be slightly more slip.
Just a thought ,
Some people in OCR changed their 1.87:1 ratio boxes for 2:1 to lower propshaft rpm from 4010 to 3750 possibly for the same reason where the prop slips X amount every rpm.