BMatthews;

Control surfaces on the front suffer from "Dynamic Instability" If you deflect the surface, it "bites into" the air and the airstream exerts a force on it in the same direction it is moving. Now the actuator has to hold opposite to keep from overtravelling. Around the center, this can flip from side to side in a big hurry and in some cases the surface can be stripped from the airframe. At best you're flapping around unpredictably putting high oscillating loads on your servo.

See the sailboat rudder comment from B.L.E.

Moving surfaces on the front of a flying control surface are a bad idea, trust me.

N