Sounds like you're good to go. 50 miles a day will be very doable for you. a 40 mile commute every day is very impressive! let's see.. 4000 cubic inches = 65.5 liters... that sounds like a reasonable amount. I think that's what my front and back panniers add up to, which is plenty for a multi day tour. Of course, it depends what kind of tourer you are. some people can cross the country with a backpack and a handlebar bag. have fun.