Wunderlich Flow Jet
Here's what I posted at the Wunderlich site.
I purchased this screen to get more air to the jacket vents. It does that well. The air used to hit me about mid shoulder. Now the air hits me mid chest. For reference, I'm just under 6' with a long torso. The stock screen turbulence was at the middle of the helmet.
The installation went fast. I have a headlight protector, so I had to cut off the points on the bottom of the screen to clear their mounts. If you didn't know it, you wouldn't miss them. I also had to do a bit if filing on the brackets.
Off road the screen is great. I don't take the F800GS on technical single track. I have lots of air hitting my chest and vents, and I stay much cooler.
At around town speeds, air is fine. The turbulence stays below the helmet, which keeps it quiet in the helmet.
Highway/Interstate speed I can not recommend. There is no bubble of calm air to get behind. When approaching speeds above 70MPH, the bike does not seem as stable as it was before. I think this is due to the asymmetric nature of the top edge. At speeds above 80MPH you have to lean into the wind to stay on the bike. I have not tried it above 85MPH, and probably won't.
Fortunately, I hate the interstate anyway.
Friend: That was some trail shortcut. Me: Yep. See how fast we got lost.