I have the 12" on mine and probably could have gone with the 14". I was still getting a good amount of turbulence and buffeting before I added my hard lowers. After adding the lowers it's nowhere near as bad. I've still got a little bit, but it's manageable.
I have the windvest 12 inch and lowers on my 10 FLTRX..... perfect for me at 5 11. I can
see over the top of the shield and no buffeting. alot of my wind turbulance was coming
from below.... the vented lower took care of that. hdman