I mentioned on here before what a believer I was in the Dynamic Balance System that Walt performed on my RV12. So after the SB...my hub had to be replaced with a new, old revised hub....things didn't seem quite the same. Sure enough, took it back to see Walt today and it was off almost as much as it was originally. Apparently just shaving those two hub sides was enough to throw it off. We had to start over...and now all is wonderful again.