I have found a problem with the tail linkage that may cause flutter, the rods that go to the inside for the elevator pushrod flex or move away from the elevator onder load so i mad a bearing for the rod where it enters the fuslage to keep it solid and strait, to do this i put oil on the rod and then used some aeropoxy mixed it up and put it around the rod and spead on the fiberglass, when it dried hard i then broke loose the rod, now have a perfect bearing around the rod and have eliminated the problem, i hope this helps, or you understand what i am saying. here are some pics.