I'm using Holman Moody VCs which use very long VC bolts and found that the VC bolt holes in my Ebock heads were either not straight or in one instance, not there at all. That's right, one bolt hole was never drilled. Guess when I found out about it?
Then the stainless bolts that came with the VCs were crap as well. I sheared one with a T handle allen wrench, guess where the rest of the bolt stayed. That was more fun.
Steve