Blocking off the PV will give you a grand total of zero extra HP.
It closes right about the time the pipe kicks in, so it's basically blocked off any time your RPM is up there, and permanently blocking it off is redundant.
What it will do, however, is cause a loss of power in low-mid range.
That being said, why would you get rid of essentially free power, regardless of how you ride?
Rogue1970's dyno runs gave proof that the engine produces power better with a properly tuned PV.
With that in mind, do you think any type of racer would willingly give up power without getting anything beneficial from it?
Even in a pure drag or hillshooting scenario, the PV is going to get you on the pipe just a tiny bit faster, and in the world of racing those tiny little bits are what add up to winning races.

If the guy is having trouble with the PV or it isn't working right, it's better to fix the PV rather than block it off.
That being said, remove the spring on the PV, stuff something solid in place of the spring, make sure it's CLOSED, then tighten the cover down on it.
That'll hold the barrel in place, and the arm can be left attached.
The actuator is only forced back by spring pressure, so it's fine if it stays connected and won't harm anything internally.