A friend of mine is also trailer shopping. There is a guy in our town named Jim Gregory who runs a bicycle powered delivery service...he moves thousands of pound of cargo--helps people move appliances (refigerators, washers and dryers, etc.) all by bicycle. He also builds bike trailers...of the industrial strength kind. His web site is
www.bikesatwork.com. It also has carfree info.
My friend is thinking of buying one of Jim's custom trailers.