I regularly ride my recumbents on rail trails and non-paved multi-use paths. I rode my BikeE recumbent pulling a BOB YAK trailer on the unmaintained Caprock Canyons Trailway. Worst parts were deep (2-3") loose sand. I can ride my Volae high-racer (650x23 tires) on a packed surface rail trail near my house,
but I prefer my Tour Easy (medium width touring tires) or BikeE (wide tires) for non-paved surfaces.

I have no experience with the C&O trail. Looking at the pictures and reading the descriptions, it looks like some sections could be challenging, but I think that would have more to do with tire choices than bike geometry.

http://bikewashington.org/canal/plan-tires.php
http://www.footprintpress.com/Articles/BikingtheCO.htm

Check out the recumbent tour journals at crazyguyonabike.com:

http://www.crazyguyonabike.com/doc/c...octype=journal

Particularly journals by Wayne Estes cover a fair amout of unpaved miles on a SWB recumbent.

Jon