If the handle straps are long enough, you can toss the duffel bag on top of a regular pack and hook one strap over your forehead like a tumpline to keep it in place.  I do that with the light duffle I use for solo trips - sits atop my G pack and I will sometimes do the tumpline thing, or just keep a hand on the straps pulled down over my shoulder.  Its easier to carry that way than at arms length, I think.