Bill hit it pretty well. When we used to setup the Hondas way back when my hair was not grey the factory guys said the screen should be the same rake as the forks or you don't make an air cusion behind it. We looked at them like deer in the headlights thinking that will slip all the air right at his head.
Didn't work that way though. It made a stream of air much more rider friendly at an upward angle thus pushing the onslaught of air the bike was pushing through up and over the riders head. By tilting the screen forward more we sent air down. The air going over the screen created lift thus drawing the air from below right into the driver.
Ever ride in a convertible? Ever notice how your hair blows forward. Thats the cusion of air. Up over the windshield then it circulates back like a bubble. Its called an air cusion. So the air from ahead of you runs up and over the cusion not the shield itself.
Mythbusters did that a year or so ago with a pick-up proving you get an air cusion in the bed when the gate is up. When you drive with the gate down you don't and actually increase resistence from the front end. result tail gate down = less fuel economy.
hmmm, where is this ramble goin, oh yeah, tilt it back as close to the rake of the forks as you can and adjust from there.
