I was reading an article the other day about just this from an older RCM issue... I will scan it and post it here after the holidays as I'm away from home.. In a nutshell. (if memory serves) it had to do with taking the distance from wheels to CG on the plans, put the nose of the craft on a scale... and correlating the distance calculation to weigth on the scale to be equal... The author said this was very very accurate and was the only way he balanced his planes. He stated the old "fingertip" method was very poor as fingers are wide and will affect balance point greatly.
Mike