I think by now Scott, you've figured out that you really need two bikes....one large dual sport and one dedicated dirt bike (with truck and/or trailer) to really be able to do some single track or high speed desert travel.
As long as you don't have to do much freeway, and stick to the <60mph back roads, a smaller, dirt oriented bike will do fine....just don't say..."hey, I'd like to ride to Tucson and back today" and expect to be comfortable...it'd be more like..."I'd like to take a week and ride the back desert roads to Tucson."
If you think you'd like to make a ride the trip, and go a bit farther away than say, a 100 mile radius, then I'd look seriously at a bigger bike...
I believe there's an old saying...It's not the arrow, it's the indian. I've seen good riders throw around 600+ lb. GSs with no problems....
I personally got really tired of being blown around on even secondary roads, having the bike pinned at 70mph, and my ******** burning like fire after 50 miles...living in AZ it seems like any trips involve a 300 mile jaunt to the destination, which is a big factor, and I got into bike travel so I didn't have to take the truck; getting 35-50 mpg rather than 15.
So...find a DR350 to pound out some trails on for $1500, and a nice R1100GS for $4000, and have the best of both worlds.....
-H-