In which position the windscreen is used, turbulence always occurs. To get less turbulence there is only one thing you can do and that is to shorten the windscreen.
There fore you need a fine-tooth saw! In the last part of the windscreen there is a spoiler, this part need to be removed. After removing this part you get less turbulence, but therefore you have some extra air pressure. This is not much but you notice the difference, every advantage has a disadvantage!
Off course you always can change the windscreen into the upper position.
It is easy removing the upper part of the windscreen, the shaped side can be polished and it has the looks like of the original.