Something else to consider is use alum. type spinners. I have had two plastic spinners explode on run up. One was "BRAND NEW" and the other had been on my Top Flight Mustang 150 size using a Satio 4-stroke for about two years then one day it went ballistic. There have been others at our field that has had plastic spinners go bad so this is why I never use plastic any more, just VERY LUCKY myself or others close by were not injured. Just another thought on safety.