I've been running the V-Stream shield that came with the bike for about 40K miles. By and large it works really well
if you keep both hands on the handlebars. The airflow requires this. If you don't, that slight change alters the airflow and buffets something awful. With the shield all the way up, for speeds up to about 70 MPH (assuming now head/tail/cross winds) it's pretty darn good. Above that speed and the buffeting gets pretty bad. A few hours out West with higher Interstate speeds left me really wishing for a
shorter shield.
To me, it's a balancing act between airflow and high frequency noise and buffeting, and I'll pretty much always avoid buffeting whenever possible.
More recently (prior to any "long" trips), I've installed a Bike-Quip shield out of the UK. 20", clear. At 60mph with the shield all the way up, there overall protection and smoothness of airflow isn't as good as the V-Stream (with both hands on the bars), but at higher speeds there isn't as much buffeting, either. More experimentation is needed.
I also have a rather wider and somewhat taller shield that came with the bike. It's a Clearview. 22.5" max height, 25.5" at the widest. Has two air vents cut out. It's a bit of a barn door. I will experiment with that as well.
Overall, I suspect I'll go the
@W0QNX route and locate some shorter shield I can cut down a bit. I vastly prefer a "smoother" airflow vs. overall protection.
For anyone in the area (or that will be in the area for a while), feel free to get ahold of me if you want to try one of the shields I have. They go on and off easily enough, and I'm happy to oblige.