Well I have no experience with the flyscreens but based on the physics reality of them I dont see how they can possibly do anywhere near as good a job as the "true" windscreens for creating the nice little quasi-vacuum for the chest, neck and face.
After a really long day with no screen if feels like someone has been steadily slapping my neck and face for hours. (essentially that is what is happening) resulting in a soreness and tightness as you fight this effect with your neck muscles and shoulders.
As it is with my Memphis Shades and the lowers the upper chest, neck and head exist in a nice little pocket of space that is free of any significant buffeting.
At 80 miles an hour if you look in your mirror with no screen at all you will see the facial muscles and neck flesh being distorted and blown about by the "G" force of that full on 80 mile an hour breeze.
With a good screen on calm day I think you could comfortably let a cigarrete dangle between your lips with no worry about it being ripped from your mouth.
Eyeglasses and wraparound sunglasses stay in place comfortably.
The inclusion of the lowers cannot be underestimated as they further reduce that bit of air/turbulence that rolls in over the tank and tends to hit you at face level.
