Did a couple of measurements on my RPM heads and I got about .300 thickness between pushrod and port, does that sound about right? I am using a 3/8"-7/16" tapered pushrod and am getting just a little contact. I also measured the side to side width of the pushrod hole and got .500. Is increasing the hole .050 considered reasonable? Actually, it appears I am just making the hole round instead of oblong. How much clearance is actually necessary?