Seeking options to carry dirt bike on back of 5'er

Other option would to put a hitch on the front of your truck and carry the dual-sport there. I would probably choose this route.

If you continue on with the idea in your first post, you may want to contact the 5th manufacturer and make sure they are OK with the added weight on the frame at the end of the trailer. That extra 100 lbs gets magnified with the bouncing that will occur back there.