Point taken- - - - -doing the vacuum gauge thing at cruise RPM with the vac advance disconnected has a much better chance of accomplishing something useful than messing around at idle speed. If the engine happens to be running under partial load on a dyno, it works very well. All you stovebolters with a dyno in your shop and a few decades of using it can probably do very well timing with a vacuum gauge!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!