ORIGINAL: da Rock
Trying to hold up, balance, and measure all at the same time is a waste of time if you want to be halfway accurate. ".
[link=http://home.mindspring.com/~the-plumber/Vanessa%20CG%20Machine.htm]The Vanessa CG Machine[/link]
I've balanced nearly anything you can think of on that thing. .40-sized Super Stick, an F6f .60 size, a Giant Aeromaster, a 33% Pitts S2S...you name it.
It's VERY simple to use. Just hang the airplane level in the loops, and the plumb bob will point directly at the current CG...simple as that. Leaves you both hands free to measure, or add/remove weight to either end, to see what the effect is.