If you're measuring at the adjuster, it's the pushrod angle that's taking away the lift. I think (just a guess on my part) that one of the reasons Hughes and Lunati Voo Doo lobes have more lift is not just to get the fast rate of lift, but to also compensate for what you lose. With hydraulic rollers this loss is the worst, and I think the last time I measured it was on the order of .024" on a .558 lift hyd roller cam. Like 1Wild, I put no more than one thread below the rocker body.