TIMTS
As Md has said the Kreuger flap is simple and effective although it does not look right which is probably what has got to you! The way I have it in my head is that deploying the Kreuger lowers the stagnation point quite markedly. This means that the amount of airflow above the stagnation streamline is increased and has to travel further on its way over the upper surface and so Mr B works better.
If the stagnation streamline is new to you let me know and I could post a simple diag