Do yourself a favor and bake that potato. I did a 60+, 14000 foot mtn bike ride last year and quarted two potatos before hand. Sealed in foil, baked for 30 minutes and gave 'em a good dash of sea salt. After they cooled, I bagged them up and stuck them in the camel back. They did a good job of supplementing calories and mixed in well with the other energy bars/gels/pb&j sandwiches. This was a 12 hour ride though, so I pigged out. I could see a plump 250 calorie potato and three bottles of 100calorie drink covering a nice 60 mile ride.