I built this rig based on a Snowbear utility trailer. I wanted the use of the trailer for transport of other stuff, plywood, etc, so I made the racks removeable with three bolts. The frame is Unistrut, a very versitile material used in the mechanical trades. ( I'm an electrician) The cost was under $100, I already had the trailer. I can haul two wood kayaks in custom cradles made of foam-lined wood, and four tupper-yaks up/top. Three bikes ride on a rack bolted to the bed sides, along with camping gear. ( The other project, in the background, is almost done)
Steve
www.steve-frederick.com