i checked out the photos, and there several road sections in several of those 100 milers, so it wouldn't be wasted miles by any means, riding the rail trail.
like i was saying this morning though, if you incorporate the game areas, you could easily put together a 100 mile loop out of mahlon with just a few road crossing. and the terrain would probably be much closer to the trails of those races, which are only partly on nice, well ridden trails like the mooch or kittatiny.
once i get my gps i'll work on mapping them out, then figure out a solid loop.