I agree that generally with the 412 we are talking bounce which is not resonance. Both cyclic position, and to a larger degree some addition of collective will help. We have found the bounce can become quite a thump particulary on wooden wellheads, where some movement of the deck allows the situation to worsen. In cases like these pilots do tend to hold the collective tightly and while they bounce, unconciously bounce the collective as well increasing the effect. I personally have not heard of this developing into resonance as such, but it does get your attention for sure. Some good technical feedback on this has come thru, Thanks guys.