I had another 3 flights with my Synergy today, I didn't notice any aileron flutter... I was really throwing it around too.
I have stronger nylon horns on mine, I notice there is still a bit of flex in the horm but nothing major. I will probably replace with something more substantial when I get around to it.

I set up point mixes so it will knife edge straight while only holding rudder input. now it flys really sweet! only needed about 4 clicks of down elevator to hold it nice and straight.