How do you folks with Rob Roy canoes portage? Mine is a Bell model.
If you share a picture, that might help.
The default is to hoist it up and place the thwart across your shoulders. A yoke makes it more comfortable, but isn’t necessary.
If you don’t have a yoke or thwart midships, you can get clamp on carry thwarts
It looks like the detachable yokes from Northstar Canoes may have enough adjustment to work on a narrow Rob Roy. You could call them and ask since they do still sell the Rob Roy. They also sell just the hardware for a detachable yoke if want to make your own (pretty easy if you start with a regular plain yoke). Swift canoe also sells a “portable yoke” that’s like a big wide piece of strong fabric (with a “v” in it for your neck) that straps around the center of the boat. You can see it on the swiftcanoe.com site under Accessories.