My advice is, don't do it. Many (most) states have laws against "wagon trains". The other issue is the well known "don't hang anything on the back of an Airstream" idiom. 75 pounds bouncing up and down, as well as the 750 pound weight that will have to be moved by stressing something on the trailer, is separation and frame problems looking for a place to happen.
Sorry to rain on your idea, but I see nothing but problems for you, if you try it.
Meddle not in the affairs of dragons, for you are crunchy, and taste good with ketchup.