Wow! I don't know where this came from. I am not using the dial indicator for measuring valve lash. I used it to find TDC on the top of the piston. I don't even understand why you would put yourself through that kind of hell. But what ever works good for you. I think Creeper's method is a good rule of thumb for finding TDC. I just like knowing the absolute TDC when doing that stuff. I guess it just makes me feel better. Feeler gauges are more than enough to measure valve lash. I am sure + or - .001" is good enough for this adjustment. Feeler gauges are a very precise way to measure. I have boxes of gauge blocks and pins in our shop to measure with. You can't fool a feeler gauge.