I may find that the hangar has not been modified to accept the Suntour, might be wrong but it looks a bit odd and one reason why the chain is not properly routed. I will have to take a closer look when I go to check out the bike later today. Should be interesting. I tend to prefer some of the early Shimano long cage derailleurs but as the Suntour is so good should just use it.
I can see that going 650b is the best option in my case, nothing like a comfortable ride!