Dick, true, throw on the aero spades and the forces drive to zero. I had neglected that.

Bill, The zero airspeed force that the surface feels is at the center of gravity of the surface. With no mass balance and with normal taper it probably is about 1/3 aft of the leading edge. If that distance corresponds to the length of the control horn located at the leading edge then it is close to the force that the servo sees. In full scale that moment plus the aero moments are totaled to give a "hinge moment" about the surface pivot. Then you can size the actuator. It doesn't matter where the hinge moment comes from, through a rotary actuator or a servo through a control hinge, it is the same magnitude of moment.

The measurement at the trailing edge is closer to 1/2 to 1/3 what the servo sees when sitting on the ground.