ORIGINAL: overbored77
Chuck, If you notice in the paragragh preceeding the one You quoted, Granelli had the engine running 1000 rpm less than peak. further richening would cause the engine to run more than 1000 less than peak, As he already had the engine running rich you would have to LEAN it to get it closer to peak.
OK, I missed that part. Since many people don't have a tach, I still think it's better to learn to set the needle by sound and pointing the nose in the air, than purely based on RPMs. This method helps confirm that the engine will not lean out and die during a steep climb, during takeoff for example.