I wonder if an inexpensive inrunner could be used? The suggested motor is an outrunner at 3500Kv. Isn't that a bit much to spin a 66mm 3 blade fan? Is the fan too heavy for an inrunner? I wonder if something like a Waldera 3200Kv or an Art-tech 3800Kv would spin a fan just as well but at 1/2 the cost.
Unknowns:
weight of fan unit
mount arrangement / distance between holes (inrunners use mount pattern for GWS 350 gearbox)
How to mount fan to inrunner shaft. Out runner shaft diam. is 2.3mm, Inrunners both have 2.0mm shaft diam.
There must be some sort of prop adapter that comes with the fan unit.

Carl