In the photos it shows a Brompton bag frame used as a flat base to rest on, clamped to the trailer frame.i have since discovered you don't even need that if you are using the carry on luggage with wheels and a handle.The luggage has a solid base and if you put bag on the axle with the bottem just behind the axle the bag's bottem forms a lip that stops the bag from sliding forward and makes it very stable once you stap it down.It also does away with having to take the time and labor to clamp Brompton luggage frame on.
My goal is to have a trailer system that i can set up in different ways to suit the situation.I can't see having to take my B&W case if I don't need it.I haven't tried it yet but I even think your trailer could be disassembled and packed inside just a carry on.