Stainless is a must no matter what. For performance and durability. 3 vs 4 blade and 7 3/16" vs 7 3/8" is more complicated with the smaller motors.

MPH and holeshot gains are usually had from working the shoe. However, rarely have I ever seen the RPM go up. I'd be curious to see what he's doing to the shoe to see any increase in RPM's.