Dick Mathis had/has a way with model airplanes. They work. I do not have any first hand experience with the Mathis Profile Stuka. However, the basics are all there. It has the right numbers, a decent airfoil, solid nose construction, straight forward construction and decent looks for a profile. Yes, it has no flaps. When you are learning/refining your pattern, there is no need for flaps. Airplanes such as this which are designed not to use flaps will give surprisingly good performance. It will fly well enough to score well against Advanced competition. (It all depends on the hand holding the handle.) I see no reason to change anything.
As Dick mentions in his article, the wing area is adequate such that flaps are not needed to "cut pretty sharp corners without stalling so most flyers will not really need flaps since few of them try super sharp corners in the first place. I suggest building it with fixed flaps, and, if you need more cornering power, modifying the flaps later." Dick Mathis knows what he is writing about.
Find a good, strong, light 35 or 40 and keep the airplane light.
Keith