Remember that the tight p-v clearance is (almost) never at TDC. The intake chases the piston down on the intake stroke, and the piston chases the exhaust valve up on the top of the exhaust stroke. You need to put your checker springs on the valves, degree the cam, and check the clearance at all around TDC to find the tight spot. .300 clearance at TDC doesn't mean squat.
You may be able to play with cam timing too. The combination I've got on my hemi doesn't let me run any more than 26 degrees on the cam. If I go any more the exhaust valves hit. I started at 28 and the v-p was nearly nothing. I found that if I backed the cam off to 26 everything came good (well good enough - it's still tight, but adequate). I figured 2 degrees off the cam was easier than fly cutting all of the pistons.
Perry