This thread is the first that came into my mind. You may ask Sower if he still uses this type of motor in his conversion and what his experience is with the heli type Neu motors.
You may want to protect the air inlets some way like this to protect the blades of the fan.
Good thing with the Neu heli motors is the air is flowing over the can to cool the motor. Lehner is pushing air through the inside of the motor which is way more critical for windings and the carbon rovings of the rotor if dirt enters via the air inlets.