Thanks for all the help. And I can assure you I am taking it very seriously.
I am in no doubt how tough it is going to be. My original temptation was to take a more southerly route through Louisville, and then Charleston WV onto Washington, and then up to New York. However, it seems the Appallachians are even more severe further south. (However, I will look at this C and O trail as it is not too late to head to Washington). Therefore, the current route is to head through Indiana and Ohio to hook up with route S at Wheeling. Would you guys suggest going even further north into PA, and taking route V through Clarion, Jefferson, Clearfield, Centre, Union etc. counties? I calculate this will add around 100 miles compared to taking route S. This will be a price worth paying if it substantially reduces the climbs (number and/or severity), but if we do the extra 100 miles and the climbs are almost as bad as on route S, then is it worth it?
I will try and get hold of the software you suggest, although I am not hugely confident in my skills in that area. And there is a limit to how finely tuned our planning can be from 3000 miles away. I would love to drive down there to take a look at some routes, but can't!. It strikes me it will be impossible to avoid significant climbs, so to bite the bullett, adjust our chainset and head across on route S is the best compromise.
Welcome your thoughts on taking route V in its entirety though.