This works great for the APC slow fly props.

I used:

A 1/4" piece of brass tube sized to fit the Nippy shaft
filler hub supplied with APC prop
#64 rubber band

You need to dis assemble the motor to install the rubber band, but this is easy to do, and you don't need to change the props that often. (see next post for details)

I shaved the corners of the 4 circular holes where the rubber band threads in and out to minimize chafing.

Pic shows what happens if you hit the ground -- prop just pops off. This has saved many props and motor mounts for me.