All due respect to everyone, but the pressure lifting the rocker shaft makes no good sense to me. The only place it can actually lift it would be right at the pedestal where the oil enters to shaft, or where it bolts down on each pedestal, and the pressure there is teenie-tiny compared to the hold down bolt's torqued tension force, as well as the rocker shaft stiffness, and the pushrod and spring forces. Speaking of which, what springs are you running, as in open seat pressure?