We used the ROB121 Robart Tail wheel Retract and the ROB165 Air Cylinder. An aluminum bracket was fabricated for mounting the cylinder to the tail wheel assembly and it slides into the existing tail wheel compartment. The only "simple" modification to the aircraft was removing the factory installed plastic tubing for the tail wheel rod that comes from the servo (the tubing, rod and servo are no longer needed). The pneumatic tail wheel assembly is a tight fit but works great and eliminates the need for a tail wheel servo and extra channel on radio transmitter. Let me know if interested in some pics of the pneumatic tail wheel project.