Biological creatures demonstrate tremendous feats of maneuverability and dexterity. Some of these feats are achieved by intelligent usage of mass and inertia. For example, lizards use their tail mass and inertia to change body pose during jumping to self-right in mid-air. In a similar fashion, having shown passive mass position effects during flight tests of both flapping only and propeller-assisted flapping platforms, usage of an actuated reaction mass is proposed as a means of improving the maneuverability of a propeller-assisted flapping wing aerial vehicle. A simplified model for equations of motion, utilized successfully for autonomous diving, is presented and adapted to describe the aerodynamic forces on the wings and other surfaces. A model to approximate the change in the center of mass to be used with the equations of motion is also described. A design using a linear actuator in concert with the platform battery as a reaction mass system was prototyped and flight tested. Using the prototype design, flight characteristics for improved maneuverability were demonstrated via both video footage and data gathered by an inertial measurement unit during the same flight.