I run the #2 -6" ! It was made that height from them. I have a clear and a Blue Ice.
I am 5' 11" and 30" inseam.
In the full up position, 4' level off it toward the rider, tape to the console buttons, it is 19 1/2".
I can see fully over it in the down position, raise it 2" still see over it and send the air over my helmet, or full up and it covers me fully. Only in debris/rain do I run it full up.
I have to say the passenger suffers though. I don't do 2 up much so not much of a concern to me. I just explain to them, hand them a full face and we go. I will raise it to full for them, but it drives me nuts.
I have a clear I cracked. It is a run out off the lower bolt hole. I was thinking about making it available to members if they want to try it.
My experience is I tried a -4 and could not see over it and it hit dead in my sight line full down. They reformed/re cut it for me to -6, and as I said, I own two. I had mine made that way. If you try to cut one, it must be from the bottom. Or you loose the lip effect that allows you to be "out" of the wind, and still see over it.
My 07 came with the factory tall. The first time I put it up I thought it was never going to stop. I had a Maxwell Smart Cone of Silence flashback. Man was it tallllll and shut you off from the sensation of riding in the wind.