The position is less of a big deal than the washers , there's posts everywhere about screen height and the secret higher position, but try the washers, cos you'll want them whatever height you go at...
The screen is held on by 2 screw on each side .
Take the screen off, and replaces the lower 2 screws with slightly longer ones (If you don't have slightly longer, you can still do it a bit, I don't )
Now shove some washers or rubber washers or whatever (with stock screws you'll struggle for more than 2, but still worth it) behind the screen, and then insert and tighten the screws.
Do that for both lower screws, and when finished, tighten the top screws more than the bottom (don't go mental though)
The other BIG deal for buffetting etc is the mirrors. Get Mirror Extenders or Aprilia Tuono mirrors (or both).
I'm 6 ft. On stock highest standard setting +2 washers, with mirror extenders and standard mirrors.
I never have my visor down, unless over about 90 (kph officer)
Worth a try, it doesny cost anything.