I found that lowering the rpms at a given cruising speed took too much power from the engine for a person my size (200 pounds) with camping gear on the bike. I can get 70 to 80 miles to the gallon, but only if I keep cruising speed between 30 and 40 or so. I invariably push faster on a long trip. Good thing the DR200 has a bigger gas tank.
I have a 16 tooth front sprocket for the 200 if anyone wants one.
Steve, maybe you could think about putting one of those orange flags on a whip on the tail of the bike...then it would be clear to traffic that you're moving slower, or they might even think you're on a bicycle.
I just kept to the extreme right when traffic came up behind me and then I would pull over if necessary to let traffic by. It didn't feel like too much of a problem. But of course that was rural Minnesota and North Dakota.