I did a test way back when with the GWS ducted fan, and it worked fine with stock Falcon 40 4-in-1, but the little motor had to really spin to keep the gyro happy. I wonder how long those tiny motor brushes would last...

Also there is a guy on the RCU - electric helis - walkera DF4 pages that did an excellent job of going to a ducted tail unit. He even made a sharp looking tail fin to incorporate the unit. Even has some pics of the finished project.

BTW I used a GWS EDF-40 motor for my test run, not sure what the other guy used but it looks like the same fan housing diameter.

Oh and, GWS makes two 40 mm fan units that I know of. THe EDF-40 is rated for voltages of 6 to 8.4 while the EDF-40H (the "H" is for high voltage) is best operated with 9.6 to 12.0 volts dc. Not sure what battery type or voltage you'll be using. FYI - My unit does have a heatsink already factory mounted onto the motor housing . The EDF-40H makes about the same thrust as the lower voltage unit but at a significantly lower amperage draw.

I buy all my GWS stuff from a place called Aeromicro dot com. Great service, prices and selection. Never had any problems with them, they even called me once about an order to make sure they sent me what I really wanted.

I wish you the best of luck with the project. Once you get it dialed in, post some pics for all of us to drool over....

Robo