I am 6' 2" and the best mod I made to my GS was to fit a GSA screen. Buffeting gone, a lot quieter and I can drive at illegal speeds with visor open.
It is an expensive solution at £300 but apart from the fact that its a solution which works it means the bike is still 100% BMW, it looks pretty good and the additional top brace means it does not shake about like the original. Fitting is simply a case of unbolting the old screen and bolting on the new kit. If you add the winglets though you need to drill some holes in the beak. I stuck some masking tape on the beak and marked the hole positions from measurements taken from a GSA in the showroom. The winglets feel a bit flimsy when fitted but have been there for six months and don't move at all in use but whether they make any real difference, I am not sure.
I looked at other, cheaper, solutions but decided that it was better to spend the money on a proper fix rather than, as others have done, try a variety of unsuccessful aftermarket solutions and have a garage stacked with useless plastic.
One I looked at was the Touratech extension but was worried about the extra strain on the screen and the big lump of aluminium in my line of sight. Finally noted that Touratech state that and extra screen brace is needed to use it and thought the cost to make the bike look crap was becoming excessive.
One plus with the GSA screen is the top brace provides a convenient place to bolt on satnav. etc. although I found my Garmin 2720 on Touratech's add-on mounting bar looked quite smart but shook about too much. Lighter kit may be OK though.
PS
Recently fitted the black GSA beak extension which does bugger all but, together with the screen adds to the GSA look. I would not pay full price but there are loads of new genuine BMW ones on eBay at silly prices. I paid £20 inc delivery. Fitting takes about 20 seconds.