I would strongly suggest to take three 60-mile days to do the C&O. A mile on the C&O trail is far more taxing on one's legs/body than a mile on the road (assuming normal terrain). And I will disagree with Spin on Harpers Ferry and Antietam as I think they are both very worthwhile, loaded with history if you're into that kind of thing. We're doing it again next September (Montour-GAP-C&O-DC) and plan on hitting up those highlights and who knows, might even take in the Ghost Tour this time around.