You can continue moving the CG aft in small steps. As you move the CG back the pitch and yaw response will increase. The limit to how far you can move the CG is when you achieve neutral stability and the plane goes where you point it without any tendency to recover when the sticks are neutralized. If you move the CG back too far the plane will become unstable and very difficult to control.

Increasing the control throws will increase control response.

Flying faster will increase control response. Control response goes up as the square of the airspeed. More power, more RPM, less drag or a higher pitch prop of smaller diameter may increase top speed. Fuel with a higher percent nitro may increase RPM and power. Use a tachometer to assist in the best needle valve adjustment. Select prop for peak horsepower not peak RPM.