[samste]

Arron just take extra care when testing as you said, prop is made from plastic and 3900kv is alot of revolutions i think and the prop will break and could be very dangerous.
Eye and Body protection if you going to try it, which you should do anyway when testing anything with props and ducted fans etc. As you don't want to get Hurt
Safety, Protection and Caution all the Time, don't risk it without it.
(Thats why i suggested sticking to lower kv but increased prop size)

Sorry if I'm scaring you or anyone else but just look on web at pictures of injuries From Rc props ducted fans etc, Fingers, eyes etc



Steve