I have 37' Norad with slides I believe when its race ready (rack on back of trailer with generator, grills and such) it is over 11k lbs. I normally pull it with a gooseneck adapter. Never had a problem with it. I also tried a B&W Companion hitch to see if pulled easier or cushioned the ride any better. This will fit into your gooseneck ball reciever and acts like a normal Kingpin/receiver set up. This works very well but for $500 I am not sure it is worth the cost for the benfit you recieve.
I am a relative newbie fifth-wheel owner, and wonder what the advantages are of the gooseneck connection, versus the normal fifth-wheel arrangement ?
We pull our 37 ' fifth wheel RV with a stock Hijacker 16K fifth-wheel hitch. Our rig has a Lippert frame, which did crack a cross-member, and the repair crew did look at our hitch while they were on-site welding up the mess. Must have been checking for a non-standard hitch so they could void the warranty !