tongue weight of a trailer should be of gross trailer weight
Tongue Weight (also called Tongue Load) is the actual weight pressing down on the hitch ball by the trailer. The recommended amount of Tongue Weight is 10-15% of the GTW. King Pin Weight (also called Pin Weight) is the actual weight pressing down on the fifth wheel hitch by the trailer. The recommended amount of King Pin Weight is 15-25% of the GTW. These weights are added to the tow vehicle's GVW.