Solidbob hit it on the head for my tire wear issue. I have a Roadsmith kit also and was experiencing the exact same tire wear pattern. It turn out that I was running too much pressure in the rear tires (not run 25 lbs.), the shocks were set too stiff, and the load adjuster was being run too low (now 25). It took me a set of tires to figure it out. Thought it was my tire size at first (225-40-ZR18 ) but I now have almost 30K on this set of tires and still have many more miles left on the tread.
I don't think there's a way to adjust the camber/caster on the rear wheels on the Roadsmith kits.
Good luck and ride safe!