I would suggest you not use the typical plastic spinners that are included with the kit or an arf. These have many problems and the new fellows soon end up discarding them.

Instead use a spinner nut like these:

http://www.advantagehobby.com/24494/DUB730/

Machined out out of aluminium they look far better and are far more functional making prop change in the field far easier. This is especially important for a trainer.

John