I've done a few experiments with having part of the control surface forward of the hinge line. My limited testing has proven to me that you do not want to exceed having 10% of the surface ahead of the hinge line or you will get severe hunting around neautral; i.e. the surface will constantly hunt for neautral and cause a tail wag or oscillation. Up to 10% though definately helps take a load off the servos. As to flutter, has little or no effect unless they are flimsy which will then cause flutter to occur more quickly. Do not confuse airodynamic balance with static balance. For static balance you can just add weight ahead of the hinge line, for airodynamic balance you need surface area ahead of the hinge line. Neither has much effect on flutter as flutter is caused by a surface going into self resonance and is strictly a function of hinge slop, soft controls (flimsy push rods) and structural stiffness. Every thing will flutter given the proper stimulus, the secret to good flight surfaces is to keep that resonant frequency out of the range at which we will be using them. Hinge gap and airodynamic balance is not part of the formulae.