An Airstream is a different breed of cat.  They build their trailers differently than regular trailers.  The standard white box trailer is built on top of the frame whereas the strength of an Airstream comes when the frame is connected to the shell of the trailer.  Regular trailers have much stronger frames because they have to support the entire trailer body.  The strength of an Airstream comes in the way the frame and the aluminum body is built as one piece, like an airplane.
The problem with an Airstream is that the rear bumpers will not support additional weight like other trailers can.  It took years before someone came up with a bike rack that can sit on the back of an Airstream.  When  you look at one you will see that it is connected to the bumper but it is also tied into the shell for support.  
These are two completely different animals.