Mine is about two or three inches below eye level. I wear an open face helmet and I have never had any problems with bugs.
The windshiled on my GL500I, which I think is stock, is that same 19" when adjusted full up. I'm trying to decide between having the top just an inch or two below eye level or right at eye level as it is now. I suppose if it is below my eyes, the occasional bug will not get deflected by the airstream and hit me in my visor, but I think that is an OK price to pay for the unobstructed visibility and maybe even a little extra breeze when riding in 100 degree desert heat.
Do most guys with full fairings have the top of the windshield above or below seated eye level?