I have a 16' trailer for my 14' flatbed John boat. When I sold my Ram and big trailer I missed having the utility of a trailer so I made a 8'x5' box out of treated lumber, took the rollers off of the trailer and bolted the box to the trailer. It has 6" sides and my boat sits on the box nicely. Now I have both a boat trailer and utility trailer! I took a 800 lb load of scrap steel to DH Griffin a couple of weeks ago, probably the heaviest load I have carried.