I just bought a new 5th Wheel. I have had one before and it came with an old hitch (don't recall the brand but it was nothing special). My new 5th wheel has a GVWR of 12,000 lbs - Dry Hitch of 1625....
The slide bar lock is a positive lock. But there could be a hang up latter on. That bar that slides might become bent to the point where it will not release the trailer when you want to unhook from your trailer. And it also will wear the bar and the king pin where they make contact with each other giving you a sloppy ride over time. I would reconsider the slide bar hitch for something else.