Next month I am planning on riding an 80 mile trip from Washington DC to Harpers Ferry WV. I will be taking a Canal Toepath trail. The trip is a steady gradual grade uphill and the terrain is gravel and dirt. Should I use my mountain bike (specialized rockhopper) or my Specialized Sirrus Sport (Basically a Flat Bar Road Bike) equipped with cycrocross tires (700c X 32mm). I'm leaning towards the Sirrus, I'm not really to keen on th idea of a 80mile trip on a mountain bike. Any opinions? My only fear is I am really going to feel the road on the Sirrus and it may become rather annoying come mile 60.