windscreen causing oscillation?

[the Ferret]

Bob one way to see where the air actually hits you is to follow the flow. Stick your left hand up behind the screen, palm forward, where you feel no air.( ie screen is blocking all the air) now raise your hand slowly until you feel the wind blast right at the top of the screen? Now keep your hand in the wind blast and slowly follow it , feeling pressure on your hand until you get to your, chest, head or helmet , where ever the wind blast takes you.on my NC Street shield EX the wind blast leads my hand directly to my eye port on my full face helmet.

You could also tape 18" long pieces of knitting yarn to the top of the shield and see where they hit you. It's actually fun to see the way the wind works behind a shield.