Wasn't a lot but enough for me, I was mainly concerned with the looks and a bit with turbulence. I then rotated the mounting a bit to get the best angle on the windshield. This did help, but found something interesting this weekend on my ride. If turbulence is the problem then take your hand at highway speed and hold it to the side of the ignition switch thumb on the tank cover and hand flat out to the sides over the tank like if you put airplane wings on the top of the gas cap cover. Feel how much air that cuts off from the driver and along with this windshield mod cut off quite a bit of the turbulence. Just as a side note I know someone here already did the same exact thing you are talking about and they were please the results.
.JPG)