I just installed a Givi A34 windscreen on my 850 special. Works pretty well at decreasing force of wind, little buffeting, but still quite a bit of wind noise. It comes only in smoke, and the fitment kit is a bit of a challenge. I plan to add an Xcreen to the top to see if that reduces noise. I had purchased a Guzzi screen when I bought the bike; looks great but doesn't work well for me over 60 mph.
Jon