Visual inspection of one of my planes recently reviealed a stress crack about 2.5 inches long from the leading edge towards the trailing in the balsa sheeting at the root rib of one of my planes. It is a World models Skyraider Mach II .40 sized sport trainer. Hmm ya think that OS 50sx swinging that 11x9 prop had anything to do with the crack?...Nah; poor craftsmanship (Just kidding World Models, I love your products.)