I'd be careful about going too small on this plane. I'm not that familiar with the GWS servo you mentioned, but you need to make sure the geartrain is strong enough to stand up to the forces of 3D flying also. If you want to go small, you can try the Hitec 225s I've had them on my Edge for about 8 months and they've worked great. Plus, on 6V, they put out 67oz of torque. They weigh 1.1oz, so you'll still save a couple of ounces over standards.

Whatever you do, get the plane built. You'll love it!