expand past the tires

This guy is building a Gypsy wagon but the trailer has sites like a utulity trailer and then he attached boards on top of the rails. One could add cabinets on both sides infront and in back of the wheels for long traips
http://www.rosettadesign.com/building_v ... pages.html
http://www.rosettadesign.com/building_v ... pages.html