The ideal timing setting is where the engine will make a long uphill pull at full throttle and close to rated HP RPM without detonating. I always make those kinds of test drives with the vacuum advance disabled, but that really isn't necessary since the vacuum at the distributor virtually disappears as soon as an acceleration load goes on the engine. The vacuum advance is only operational at light-throttle cruise.
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!