OP here.
I think I would like to clarify something here. I think there is some confusion and I'm not sure it's been addressed correctly.
These are gooseneck receiver to fifth wheel hitch adapters... These being Andersen Aluminum Ultimate, B&W Turnover ball Companion fifth wheel hitch, the Cequent High Rise, and the Curt X5 fifth wheel rail Adaptor.
They ABSOLUTLY use the floor of the truck bed to transfer some of the weight to the truck frame.
The Andersen design uses a bolt to Draw Down the hitch onto the gooseneck ball making them essentially one unit. The Companion Operates similarly except by replacing the ball with a Seperate shank for the B&W receiver. Same for the High Rise... All three uses some kind of draw down system to make the receiver and the hitch one solid unit.
The Curt X5 doesn't have a draw down feature and some users have reported some movement in the rails that need to be shimmed out to make the rails really secure.
In theory, I dislike the X5 the most as it gives the most opportunity for movement, reality seems to be when 1-2 tons of weight is bearing down on the X5 it is pretty well locked in.
In summary, Gooseneck to fifth wheel hitches are systems that use the gooseneck receiver, the fifth wheel hitch, AND the bed of the truck to transfer weight and force to the frame of the truck.
You can see in
this Video some flexing with this companion. Note that the Companion itself is not torquing.... The Turn Over Ball receiver is flexing.
I suspect that under similar circumstances the Andersen will flex a gooseneck receiver... But as I am not a user I do not know. But the reported bed dents (Andersen Ultimate has these reports too) indicate that the gooseneck receiver does indeed flex.
thanks,
Jeremiah