PCV- Good or bad idea for a performance engine?

The PCV valve will "blow closed" in this situation, so your engine will not become overwhelmed by oil vapors at wide open throttle. Besides, think of the relative size of the little 3/8" hose compared to those 4 wide open barrels of your carb. Thats where the mixture comes from. Besides, blow-by IS air fuel mixture that didn't get burned the first time.

You can always splice a 3/8" universal metal cased fuel filter into the PCV line to catch liquid oil. Dump it out every now and then to figure out how much oil is being expelled.

If you ring fit is as poor as you indicate, your engine is possibly not healthy enough to be consistent in American style bracket racing (I don't know what you run down under) so the slight effect the PCV system may have is the least of your trouble. You will in fact have greater oil control issues due to the rings. What is your oil consumption rate?

Racing a tired engine like that runs the risk of NEEDING that rebuild well before next year. But do go have fun with it.