Hitch Extension Questions for Pulling a 7 x 14 Cargo Trailer

I think you are underestimating 325 lbs of hitch weight on a 4200 lb trailer. It will probably be closer to 500 lbs which is the cutoff where I start pointing people to a SuperHitch and SuperTruss.

It's not just the strength of the double truss extension that gives Torklift such high ratings when using an extension. The receiver uses thicker and deeper reaching side plates and a larger diameter cross tube holding the dual receiver ports.