Travoy can be tippy and loads the seatpost in ways that does not please Brompton Inc.
A good way to assess trailers is to video them under load with rear facing camera
The Travoy is pretty flexy and where it CAN be loaded down (nobody stops you). It has plastic hinges that flex a lot under load.
Most trailers get overloaded, so plan on that, cuz that's where awkwardness happens.
Personally I like axle trailer mounts and have a bob and a Cruiser
the IGH makes the Bob a big project on a Brommie