You may need to reinforce the rear frame to carry the weight. Keep in mind the weight transfer from tongue to rear. check this page out it has what you are thinking about with the 5th wheel. The ultimate single wheel trailer system.
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Retired Navy
Jake my sidekick (yellow Lab) 10/04 - 05/20
2017 RAM 2500 CC 4X4 Cummins Diesel
2016 Flagstaff 26 FKWS
AF&AM & El Korah Shrine of Idaho