OK chaps, an aerodynamics theory numpty here(and apologies if it's too far off the original topic) but:
I'm happy with my Leviosa for anything in PO9, and FO9,but myAbbra,by comparison, def lacks rudder authority for the rollers and the K/E loop.
I tried a canaliser, and, whilst the Rudder authority was certainly improved, the other effects on the model set-up threw everything out so much that I gave up with it.
Would it be worth trying just a dorsal fin, without the little wing?