I purchased a MP Jet AC 28/7-30D Mk2 Outrunner Brushless Motor
from Hobby Lobby for my Alfa P47 and am having a lot of trouble with prop adapters. I've purchased two E-Flight 3mm colleted prop adapters and one Great Planes adapter. The first E-Flight stripped on the first try (I'm very displeased with their quality) and neither the GP or the second E-Flight will tighten down all the way. I tightened
those suckers down...to the point that you can start to see the APC props compress, but I can still turn the motor (I can see the shaft turning) while holding the prop still with a little effort.
I'm used to the feel of my Eskay motor/GP prop adapter combo. That is rock solid tight.