Surprisingly the very small screen works for me at speed not higher than 80 miles/hour. And my wife underlines that she does not feel turbulence as she did on our 2007 Rocket.
I am not tall (5'8") and she is 5'7".
We had a Madstad screen on a previous bike and there are a few things to take into account to get maximum efficiency:
- lower part of the screen should fully cover the "plate" above the lights to create a flow of air, between this plate and the screen, which will be oriented above your helmet
- total length of the screen should be able to reach a line between your nose and your chin.
- Try to take a picture when you are sitting on the bike with the screen in order to choose the length of the screen, then to adjust the angle of the screen
- From my previous experience, an angle between 55° and 60° vs horizontal was optimum. Unfortunately the plate above the lights on the bike (apologize I do not know the name in English) has an angle close to 40° which is too low to create a great flow of air with the windscreen at 55°.
I was a bit lazy to create a drawing, but if anybody is interested I can do it.