RE: What is flutter?
Good point daRock! 'tis one of the reasons that throttle control and/or a speed limiting large diameter low pitch prop must be used on planes designed for 3-D aerobatics.
Another thing to avoid is a round trailing edge on a control surface. Sharp pointed wedge is ideal but impractical because it gets damaged so easily. Almost a good but a lot more practical is a wedge shape with a squared off trailing edge.