Set up your linkages so that you use full deflection of the servo and less deflection on the surface. Sometimes when you setup a plane for 50-60 degrees of throw your also throwing out the resolution because your getting less movement at the servo in order to move the surface so far. In other words do you want the plane to fly well, center well and be well tamed or do you want 70 degrees of throw and have a plane that you constantly fight to fly level? Most planes really don't need that much throw to 3D so settle for something in the middle and enjoy it.

Does this make any sence?