Well, I dont know if Im much help or not, but I prefer less wind, which means a windshield of decent proportions.
My Z1000 was naked, no screen really to speak of, but it had a small deflector that kept the bugs off my chest.
Went from that to a VTX1800 and a NC Switchblade 2-up shield with lowers and man was that nice on the highway!
I loved that I could take it off in a matter of seconds for around town though.
Currently, Ive got a Rifle base on the way, and plan to make the upper shield from a GW1200 shield, similar to the mega-shield Ive seen in pics that someone else made, and also plan to add the GW vent to it as well...saw it gave nice airflow on hot days on that particular set-up...hoping it works for me too!