Still using a Gooseneck adapter on my Fiver since 2007.
Currently using the Reese Goosebox. Not entirely happy with it. Must air up airbag every trip (use on rough roads may "puff" the air out the overpressure valve on the bag) and it fills very slowly. They also want you to grease the pivot point on the ball connection every trip. More maintenance than is reasonable in my view and NOT fully disclosed in their advertising.
Miss my old Star Performance Kingpin (Gooseneck) adapter (Highly recommend this adapter as the glider motion alleviates almost all stresses), but VERY VERY rough Interstate roads in New Orleans bent the kingpin plate on the RV Hitch (Adapter stronger than the Lippert Hitch) so I decided to try the Goosebox, which was not much more expensive than a new pinbox.