I agree that spinner problem would eat up some of your flight time. I've never ran a Prop Nut, so I cant say yay or nay. BUT, a plastic spinner vs. an aluminium on a trainer plane and a newbie on the stick.....I say plastic. Reason being is a plastic one will disperse most of the impact on a hard nose in. The result would be a broken prop and broken spinner (easily replaced). Now the aluminium spinner on the other hand will MOST likely bend the crank. Now if you look at it that way then messing around with a plastic spinner and losin' a little flight time vs. bent crank, seems obvious to me. Besides, a beginner is going to have to learn to work on puttin on a new prop every now and again. I wouldnt want to tell a beginner that he needs to do a coplet motor tear down B/C of a bent crank. Just my $.02, dont want to make anyone mad.