as I'm looking to windshield installation, the most important thing for me is comfortable ride and weather protection.
I have italian kappa screen 440A 66x64 cm.
It's protecting my hands and directing airflow over my helmet. a few cm higher screen would be better as I'm 184cm high.
haven't noticed any improvements in mph/mpg but made my everyday riding much more comfortable.
at constant rain at 40mph ride during 20minutes almost all my body was dry. I'm also using leg cover.
But, driving behing anything bigger than renault kangoo, preugeot partner.... is making turbulence.
driving behind lorries and bigger trailer trucks is a nightmare
also, as I have open face helmet, it is protecting me against bugs, debree and rocks
http://www.kappamoto.com/My-motorcycle/?ma=KYMCO&mo=Agility-50-125-150-R16-08--12