I am in the process of building a Stuka with the 'exposed' ailerons and flaps. I believe there was also a German tri-motor, WW II vintage, that had the similar surfaces. I'm finishing up a Fiesler 'Storch' which has what I guess you'd call slotted ailerons and flaps. Some Storchs also had a secondary elevator surface mounted below and slightly forward of the elevator. Wondering why these surfaces appeared, and disappeared from the scene? It seems like these were pretty successful for their time-and maybe that's the answer! Interesting design features though. Any thoughts on the subject?