Things have been very well with my 110 except for some kind of vibration. It shows up mostly at the rear crutch / tail boom area at certian rpms (not full throttle). I experienced a crash sometime ago and the crutch was damaged. I repaired the break with a carbon fiber cloth/ superglue patch. I don't want to replace the crutch because I'm holding out for the aluminum one from L.M. if it ever comes out. The main rotor shaft appears straight and I have replaced the tail boom. The tail rotor drive wire is straight. The only thing I've noticed is "slop" on the main shaft/main rotor mounting. You can hold the main rotor with one hand and turn the main rotor gear for some distance with the other. It appears that the bolt or main shaft slot are worn. Would this cause a vibration? How much slop is normal? The heli flies great even with the vibration, I'm just afraid it may damage something else.