With the stock windshield on my '16 SGS I couldn't go above 70 without the head buffeting rattling me around so hard it felt like my vision was cutting in and out. Within the first 100 miles I went to the local aftermarket shop and tried the 6.5" and 8.5" Klock Werks Flare windshields.
I'm 5'10, and the 6.5" did a sufficient job of throwing the air over my head when in the normal riding position, and looked best on the bike. But I ride long distances on the weekends, and when I stretched my back totally upright when riding my head would be back in the buffet zone. I'm more of a function over aesthetics kind of guy, and figuring that I may one day get an aftermarket seat that raised me up a bit, I went with the 8.5" shield.
I hear the radio better, I can see over it perfectly with the stock seat, it still looks pretty sharp, and it throws the turbulent air clear over my head so I can ride at any speed in comfort. The only thing of note, is that it does tend to rattle just a bit when starting to move from a stop when the bike experiences the most vibration. Since it's only every so often, and often inaudible if my radio is turned up, I don't mind as the pros far outweigh that nitpick of a con. That being said, if I ever have to replace it, I'll try to put a super thin rubber strip on the front and back of the base to try and prevent that rattle.