just for clarification ... there are "goose neck adapters" which extend the 5th kingpin leg down to the goose neck ball, which add additional torque on the 5th wheel frame. Those tend to void the frame mfg warranties.
Then there are other hitches which really are not "goose neck adapters" (Andersen, Reese, B&W) which attach to the goose neck ball, but raise the mounting point up to the 5th king pin, and do not add additional torque to the 5th frame. Those are generally accepted by the frame mfg and may not void the warranties.
I have the Andersen Ultimate and couldn't be happier. Coupled with the goose neck turn over ball, I have a flat, empty bed when not towing, retain the goose neck ball for GN trailers, and have a very easy hitch to move about for 5ers.
