Hello!
I see people constantly getting bikes that are too big for their purposes, just because their friends say their smaller bike can't make it up a hill, or other things they know nothing about. Here, let me show you the truth about small bikes and long trips!
http://www.youtube.com/watch?v=2wJhlhT6i2QNow that we have that out of the way, I should tell you that it is very important to be comfortable on a long trip with a small bike, so get support on that back of yours, and you can get throttle rockers, so you can relax your hands, etc.
I have been told a Honda Rebel can run 70MPH, but that it needs to rest a bit doing that. What I recommend is to not run full throttle, and to back it if 1/3 on those trips. The engine will last a heck of a lot better, and you won't stress this tough little engine so badly.