I'm no longer happy with checking it on the rocker. Even when as close as parallel with the lash adjuster as possible. There's usually a multiplication factor involved and it is always ambiguous. The next way I'm going to try involves yet more tools. I think it's important to read right on the lash adjuster, thru the rocker arm, with a very small or very pointed dial indicator tip. If you have that multiplication factor in the mix you are wanking off in front of a fan.