Split flaps, interesting! More drag than any other attachment. Was described once to me that the wing has good enough aerodynamic qualities for the entire envelope so the need for only split flaps. 402 and 402B have split flaps as well. 404 went to fowlers. This goes the same for me as trying to explain how those barn door Kruger Flaps actually increase lift???? swinging forward from under the leading edge??? dropping vertically down??? Wouldn't that kill any smooth flow? Does the turbulent air behind the flap, both Split and Kruger, form a boundary that acts like an airfoil shape?