Use the cam grinder's specification, as they know what clearance ramp they put on the cam when it was made. Always do a valve adjustment on a fully warmed-up engine, and if necessary stop halfway along and run the engine a few minutes to keep the temp up to normal. I absolutely do not like trying to adjust valves on a running engine. With a little practice you can do a companion cylinder valve adjustment on a stovebolt engine in 15 minutes or so with perfect accuracy.
For an engine that pulls hard a lot of the time, just increase the lash adjustment by .001" or .002"- - - -a little rattle is better than burning a valve from not enough clearance. Just don't get radical on increasing the gap for some imaginary difference in performance- - - -it just ain't gonna happen!
I remember reading the same info on altering clearance specs from Isky in the mid-1950's. They were using that method to compensate for cam grinding errors back when all camshaft grinding machines used a mechanical "master cam" to set the lobe profile. Today's CNC grinders are much more accurate, so the old "alter the clearance" compensation while degreeing the cam is as obsolete as caveman Og's stone axe!
Jerry
