I also have the same plane, same 7 servos, and the digitals on the wing. They also chatter with no ill affects. I read a few threads on RCU that say this is normal. I have read that it is just the weight of the aelerons and flaps pushing down on the servo and the servo responding to keep them level. I do not know if this is fact or not, but most responses to this question that I have seen say the same.