I assume you've tried adjusting the low limit screw? Sheldon Brown has a good write-up here:
http://www.sheldonbrown.com/derailer-adjustment.html. Maybe you can adjust it so you get no rubbing in the lowest gear (which you'll likely use on tour) but you will have some rubbing in the highest gear (which you're less likely to use)?
You're bike looks a lot like the one I'm building up. That's an interesting looking handlebar bag, care to elaborate on it? How is it mounted?