8"x11 Lbs cee is sufecient but for the same money you can use 3"x6"x 3/16ths rectanger tube for added strength and ease of construction. IMO goose tongues are usually overbuilt and here's reasons I've come to this conclusion. (A) Specs for any type steel are hard to find in print and if you find specs someone paid an engineer to draw up,only an engineer can understand them well enough to use them for other than purpose engineer drawed them up for (bridge,skyscraper,semi trailer ect). (B) If and when a mfgr hire's an engineer to desighn a utility trailer with minimunm size material,it will do the job if not subjected to neglect and abuse. The mfgr's insurance company know's the trailers might be mis-used resulting in failure so they will not cover it unless built to double specs. The same insurer will cover lesser built rv frames since they are far more unlikly to be neglected and abused. Examine a 15k Lb travel trailer and you will see it's no where near heavy as a utility trailer. It's your trailer. If you inteend taking out fence posts small trees then not inspect before taking it on the freeway,do what mfgrs do. If you will treat it likeyou should,save fuel by not making it heavier than required to carry loads. Many will disagree so you have to decide how you feel. While I have the flame suit on I may as well stoke the flames even farthar. Most want the trailer to be rigid and not flex when stressed. I intentionally build flex in so that stress is spread rather than concentrated on a single joint or member. Watch a semi tractor and trailer frame as they cross a ditch. For that matter,watch your 3/4 ton truck frame as all four wheels are on different elivations.
