I have NEVER seen one shatter in my 12 yrs. let alone SEVERAL IN ONE DAY!... Glad I do not fly at your Field! , BTW were any of them the cheep ones that come with most of the ARF's?

I think that Art is on the right track, dont let the blades touch the cone. As for the safety glasses.......They have been putting stickers on Prop's for years, how many people do you know that wear "safety" glasses? My sun glasses meet ANSI. but they are safety glasses that have dark lenses (Smith&Wesson shooting glasses)