I thought just to do a little update.
Lower screen is still on top holes. I'm yet to try another ones. But today, just out of curiosity, I tried lowering the top screen. I was riding, watching the screen and thinking; this screen is known for Givi's patent of "compression box" between two screens. The more you lower the top screen, the bigger gets overlapped area between screens and bigger gets compression box. So, as there was more air to be compressed and higher pressure from now bigger box, that may shoot the air even higher verticaly and give me even better result. So, I pulled over and lowered top screen just a notch bellow the middle of the sliders:
WOW, much better, much cleaner flow.
So, this Givi Airflow is like a toy, you just keep on playing with it... I will...