I ride the GSA adventure with seat set on high setting, and am also 6'4" tall. I have tried the following:-
Wunderlich Adjustable Screen extension (from NN): Reduces the most noise, but looks the worst. Buffeting reduction on par with the GS one.
Touratech lockable Screen Extension for
GS: Nearly as good as the Wunderlich one for noise reduction, buffeting reduction same as the Wunderlich one, but looks loads better than the Wunderlich one.
Touratech locakable Screen extension for
GSA: By far the best looking, but by far the worst performance wise.
Just to point out though that none of the options above make it perfect, but do improve it 50-70%. However, use one of those and put the seat on hte low setting and all becomes eerily quiet. I don't ride like this though as I prefer the extra leg room.
I decided not to try the laminar lip as it looks like it's a permanent fitting?
From left to right: Wunderlich, TT GS, TT GSA
From Left to right; TT GS, TT GSA, Wunderlich