The Super Sportster (any size) is designed for moderate to high speeds. 3D is performed at very low speeds. The Sportster has small ailerons, an airfoil that will separate (stall) at moderate angles of attack and a relatively high wing loading. On top of that, the design of the elevators makes them prone to flutter, even at low deflections.

The Super Sportster is a GREAT sport plane, but if you were trying to list the ten worst airplanes for 3D, the Super Sportster would be on the list.

Jim