Rick Martin proposed this route:
I plan to run a double crossing of the Cumberland Valley portion of the Appalachian Trail. I will run the valley “rim” to “rim” to “rim”, which is a few kilometers shy of 60k. In order to reach the symbolic 60k distance, I plan on leaving the Boiling Springs forge parking lot at 8 am to run up to the first “rim”….Center Point Knob. I will then run across the valley to the next “rim”; the high point near the Darlington shelter. I will then turn around and run back across the valley to Center Point Knob. The final stretch will be back to my car at the Boiling Springs forge parking lot; hopefully by 4 pm. Link to the course…. footpathapp.com/routes/752bacb8534549719c07...
This one is on my list to try.