Single cylinder gassers are a little prone to vibration issues, which is one of the reason so many go to such great lengths in prop balancing. I'm sure that you already balance the blades of a prop but do you also balance the hub? That's often a source of troubling vibration. If not, there's a pretty good video on prop balancing located at down on the deck. As for experience with your type of engine, no I do not have any.