I had similar issues with the stock screen. Im 6ft2 &it puts turbulent air and wind around my lid on all positions.
I tried the givi screen which works ok but is massive. I look through the screen rather than over it. Its not ideal in windy conditions either.
I also bought another stock screen from ebay & cut it down. This actually works quite well for me. Obviously not as much protection but I had no noticeable turbulence or buffeting. It doesnt quite suit the lines of the bike though and my cutting skills need improvement ha. I still put it on occasionally if the weathers gonna be decent.
I re-drilled the holes on an mra vario touring screen I had from my old mark one versys & fitted that. I had it on for nearly a year.
That was a compromise between protection & buffetting. I think I just got used to it in the end and I eventually got the vario mk3 version which is on now.
Ideally i think small is the way to go. the stock screen is already quite small but could do with being a couple of inches shorter. like i said above cutting it down doesnt look quite right.
Ive had numerous screens over my mk1 and this mk 3 versys and none of them are perfect. Ive even tried adjustable brackets. I see posts on numerous forums & lots of people have the same issues, although a few do find a setup where they are happy. I think its worse if your tall & earplugs are a must.
I try to find a happy medium now and stick with that.