Let's take it easy here...What were those "great difficulties" here in your opinion? Please remember 109 developed whole time and K4 was almost totally different plane when compared E4 for example. Different wings, ailerons, rudder for example. 109 was actually one of the easiest ww2 planes to fly. Only very high speed manouvers were bit problematic because controls became stiff but it was not only plane with this problem, for example Mustang had similar problems too. In take-offs and landings 109 needed some careful treatment but again, once you know what to do there was no big problems and K4 should not be any more difficult here than say G6, actually K might be bit better because wider wheels and longer tail wheel.