I have been using the Reese R16 slider with a standard kingpin for about 6 months now. Compared to my 13 year old Reese 15K slider it is smoother, the tolerance on the jaws is very tight with no noticeable movement. You do get some movement from the round tube slider, but I found that you can eliminate it by making sure that your brake controller is set correctly.
The round tube slider slides much easier than my old square tube did. That said I think the addition of the MorRyde pin box would be a plus, I am looking at one for my 5er.
One other thing, the R16 slider does not allow you to use the bottom adjustment holes to lower the height of the hitch, I have a 2013 Chevy 3500 2 wheel drive and with the hitch set as low as I can get it I have 8" clearance at the bed rails(which is good) but I am about 2" nose high, rather than change my kingpin height I plan on moving my spring pack to the lower hole on the hanger bracket.
