RE: Tail Flutter..
Scythe.
I test flew a clubmates Synergy 90 3D a few weeks ago (YS 110) and also suffered from tail flutter. Engine at about half throttle. Cut the engine straight away and landed quickly. Once on the ground we could see that the tailplane on both sides had cracked about half span. Photos have been sent to the distributor here in the UK, and he is awaiting a reply / explanation.