I ended up ordering the +8" Cee Bailey windsheild, i received it four days ago. I tried it for a day and i found IF i crouched just a little and remember i said IF, the protection was excellent. There was no turbulence or buffetting on the top of the helmet. The wind noise was cut in half and the wind blast on the upper body and head was absolutely gone. This created a very serene riding experience. I could ride with the visor opened or closed. Up to 160km/hr, the bike was still stable and unaffected, i don't normally ride at these speeds so i didn't try to go any faster so i couldn't tell you how it handled at higher speeds. When i did crouch just this little bit i was still looking over the windsheild. If i sit normally, the top of the windsheild would line up right between my chin and lower lip, this was about 4"- 4 1/2" below my eyes. When i crouched a little, the windsheild was about 2" below my eyes.
Now, if i sat in my regular position, the ride was almost unbearable. With my full face helmet on with the visor closed, there was a small but annoying buffetting. This was bearable but the vibrations pulses that i got simply was not acceptable. Now if i rode with the visor 3/4 open, the vibrations pulses disappeared and the buffetting was lessened. I guess the angle of the open visor deflected the air hitting the helmet, this caused the vibrations to disappear but the buffetting was still there a bit and the open visor caused more wind noise. So i couldn't get quite comfortable riding in my regular position, i needed a couple of inches to make it right.
I called the guys at Cee Bailey's and explained what i experienced and that i would like to return the +8" and get a +10" windsheild. They were very good to deal with, so by the end of next week, i will have the +10" windsheild. Hopefully this length will be about perfect. Keep in mind i am only 5'11" but i guess i'm long trunked.
I will give another report when i try the +10 windsheild.