Don't know if you guys are still having problems with the Kavan props but I recently had my first nylon prop fail. It was a Grish 12x4, and the prop literally blew apart when I went to full throttle right after starting the engine (luckily nobody got hurt). Everybody (myself included) always got a kick out of the way these props wobbled around at idle and low speed and since all of my nylon props did it, I never paid any attention to it. Looking back, although I check balance on all my props I think maybe the nylon props may be more sensitive to proper balance as they do flex alot (Irvine specifically states not to use nylon props because of this).

Mike