Good luck. I hope the 5th is a toy hauler. I did the same thing. Built a $3,000 swivel wheel. Got stopped. Not legal in Fl and many other states. It may be legal where you live but then you have to stay under the length laws in every state you go into. If you are going to tow a swivel then build it yourself it's much cheaper and better quality.
Bill & Linda. If it doesn't move and should, WD-40 it. If it moves and shouldn't, duct tape it. F-350 dually, 40' Sunnybrook Titan toy hauler and custom Harley