Valve Adjustment, backside method

Vehicle Information: Model: 911 SC; Year: 1979; Body Type: Coupe; Total Mileage: 142,000;

I have just read about a "backside" method for adjusting the valves. It basically describes using a "go" "no-go" method and measuring with a 2.5 and 3 thousandths feeler gauges at the point where the rocker meets the low side of the cam lobe.Have you heard of this method? Is it a valid way to check (and adjust) the clearances?Thanks,mnorrell