My Carry-Freedom City, folds flat within its own squarish frame.
it includes a big sling bag that hangs in the frame in travel
or on you when the bike is packed for shipping.
or multi modal travel..

if there is a second duffle, it lays nicely tied on top of the sling bag.

I can also carry my folded up Brompton on top of the trailer.. might be useful if
you have to catch a car on a train on the opposite end of the platform..