for Dusts cut the center ribs out for servos, point the horns outwards to have the control horns as far out as possible with straight control rod runs. this also hides the servos out of the airflow at the same time. ( dont link the control rod to the bottom servo arm, and horn on the elevon upper surface, it leads to bad flutter, even on 30mph funflys, ask me how i know
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after that as long as you seal the hinges on DD, any flutter you get on either plane is your fault for not using strong enough servos or control rods