I was thinking about it. Coleman has a nice, light backpack with a 2 liter hydration bladder and plenty of room for other stuff.

I didnt know if it would ache the back on long tours AND the major downside seemed like it would make you too hot in the summer months, but I dont know.

It would be a nice place to keep the valuables, or do you just run a handlebar bag instead and keep all your water mounted below?