i'm 6'2 and it seemed to take the air from directly in the face, to just the tip of my head. i've never really had the buffeting problem, with or without a helmet - maybe my melon's too big. you'll want to temporarily put the lip in place with tape (tape the crap out of it, so it doesn't fly off), then when you get it where you want it, mark the back of the windshield with a dryerase pen, then you can apply the self adhesive strips that they supply with the kit.