take a look at the Craig Vetter Alcan fairing project.
Vetter-Alcan-fairing I spoke to him about it when I rode in the 2011 Mid-Ohio challenge. I was 7th and the best stock bike there. I also was the only one carrying anything resembling the 4 bags of groceries. I had 5 days worth of camping gear as I was on my way to the BMW rally in PA.
2011 Mid Ohio Craig Vetter Fuel Economy Challenge results
Craig had made the prototype Alcan out of aluminium. He said it reflected engine noise, and since you were out of the air stream you felt more heat. Temps were over 100 degrees (hit 104 one day) and riding on the bike in the air was grueling that weekend headed to PA and back to TN. I gave up the idea of a high MPG bike since I have to be socially acceptable when I get to my destination most days. Dual sport you are not going fast enough to need the aero, unless you are traveling a long distance to hit a trail, like riding from central USA to the north of Alaska on the Al-Can HWY.
I think someone in the North East got the fairing from Craig and was going to work on it. Craig and I discussed the use of sound deadening foam to cut down the noise reflection. Think about being in the focal point of a parabolic mirror. it would need it. Streamlined panniers with a Kamm tail might help a bit. Like has been mentioned, you will need to leave room for body english when you off road the bike. Also remember the crash bars and panniers strong enough to support the weight. Mine has taken a few dirt naps without damage.
I have tried all kinds of screens trying to find something that didn't buffet. Being in the wind has been the best so far, altho the Ztechniques VStreamŪ Tall Touring Screen for F650GS/G650GS Single held the most promise, but my handlebar risers hit the screen.
National Cycle
I started to fabricate a way to mount a K1200rs screen but some health issues have nipped my bike riding for a bit. Notice the lower wings the VStream screen has. Similar wings, as well as vents to let some air in the rider zone are on factory BMW's that seem to not have the buffeting most larger screens have.
To find all kind of info on the 650 thumpers,
F650.com Home
so, yeah, there has been some thoughts on this subject.
good luck, have fun