Are you looking for a que sheet or gpx/tcx file? I've done a couple of routes over the Sagamore and down that links into the Cape Cod Railway Trail (CCRT) for some distance, but you can't ride it all the way. On the return it heads toward Hyannis, so if you stay on too long you add extra distance to your ride. One way is about 65-70 miles from Sag depending on route. You can ride either side of the CC Canal trail from Bourne/B-Bay to pick up the route at Sagamore.
Most of the courses use similar routes on 6/6A at various points. Those that don't use the CCRT criss cross it at points.
If you need a que sheet I might be able to dump one of my rides into bikeroutetoaster.com and post a link. If you need an electronic file, search gramin connect, map my ride, etc. and there are routes up there already.
Have fun!