Dick, its quite clear we must have flown them too fast - too fast for the design of the ailerons/wing that is. The tail doesent flutter at the speeds we have flown them at, just the ailerons. Its crazy that the design allows flutter at the airspeeds we attained. I don't dispute the purpose of the plane just the margin for error built into the design. I have never had flutter on any of the ARF's or kit built planes I have built. My Tower Uproar handles full power dives without any, as did my H9 Twist. Sure they are both small planes in comparison but the designs have no quirks and flutter simply doesnt occur even at insane speeds.

Being forwarned about the F90 we took precautions - better than std servos, taking care with throttle control, linkages etc. and still we fluttered. There's no margin for error or varying prop pitch to set a motor up etc. Thats bad.

Also, looking at the Seagull Harrier, its smaller than the F90 but lists a 90 as minimum size. I'm wiling to bet it won't exhibit the same flutter characteristics at all. The wing is very different and I bet the ailerons are lighter than the F90's.

I am very interetsed to see how my balancers affect the flutter problem altho with a non stock control horn it will be impossible to say which mod worked.