The Vanessa rig is a lovely thing but it still won't tell you how the model will fly best. It gets you to the designer's recommended balance point, but you may not fly like the designer, share his tastes in handling or have your gear in the same positions.

Finger-tips get you close (I use it on models up to 18 pounds) but flying is the only way to tell you are where you need to be. Does the nose rise or fall in knife edge? If you fly a 45° upline and release the sticks with the model trimmed for level does it fall or climb? How about the same maneuver inverted?

Preferred center of gravity is a personal thing.