I store the CF city inside the Burly Flatbed in the closet.
the city is almost as wide as the flatbed, just the wheels are underneath the outer rim.
the 2 wheels on the flat bed are outside of it's cargo area..

Big watertight Duffle like Ortlieb's rack pack can add to the capacity of the City,
lay on top .. I found a Cascade designs 'pro' portage pack ,
that will drop into the load area of either,
and it has a set of backpack straps, to wear the trailer and bag..

normally a bag to wear while carrying your canoe, upside down on your shoulders
between lakes or streams.