I know it is getting more expensive but... You could got to a real Servo Motor or Stepper Motor driven head. Hobby servos work well with light loads, or you can go for an expensive RETRACT servo, but a stepper or servo motor will give you more motion options. Balancing is still an important consideration. The only problem with balancing is that you are adding more mass and the hobby servo will have to deal with making that greater mass move. More Acceleration forces.