I do not want to hijack this posting but we have a similar problem.
We have the Demco AutoSlide hitch. The new to us 5th wheel came with a MORryde pin box. On the first trip of 400 miles we noticed that there was movement with both the pin box and the hitch. I do not know if this was good or bad but I was concerned that the hitch and the pin box may be working against each other and not as a team. After searching the Internet there was a recommendation from people who had the same combination to add a special plate to the hitch. In a discussion with the autoslide hitch technical support they suggested a different wedge plate to reduce the side-to-side motion from the pin box. We have not installed this new wedge plate but is my understanding that this plate will still allow front-to-back motion by the morryde pin box.
I would suggest that MRAD talk to the technical support at both Morryde and Pullrite.
Does anyone have experience with the Demko autoslide hitch and the morryde pin box, if so what has been your experience after adding the wedge plate.