You've got the right idea but the wrong way to implement it. If you leave the hinge and pivot axis at the 50% point you're in for a world of hurt and likely a whole lot of flutter.

The center of aerodynamic torques on a symetrical airfoil or a flat plate actually occurs at around the 25% point when air is flowing over the leading edge up to some fairly high angles. This is why if you try to glide a sheet of balsa it'll immediately flip up or down (depending on the angle of attack you launch it with) and happily rotate itself all the way to the ground. Through a fancy set of sketches this can be shown to be because of the fact that the CG is at the 50% chord point but all the aerodynamic force is at the 25% point. So to truly reduce your servo load to the absolute minimum you need to put your hinge axis at the 25% point. If you find drawings of the Skyservant that are detailed enough you'll find that the full sized axis is at or just a % or two in front of the 25% point for just this reason.

Hopefully it's not too late to move it because if you leave it where it is you WILL need a huge servo to control it. Even then that won't cure the very likely flutter issue you'll have.