And there is this:
https://www.amazon.com/Companion-5th...e%2C108&sr=1-2
I bought a 13K# 5th wheel in 1998, and towed it with my F350 gasser with a "lil Rocker" hitch until I bought my F350 diesel in 2007. It already had a B&W gooseneck "plate" installed so rather than pay $1000 for a "Companion" hitch I got a heavy duty adaptor for my 13K# trailer, and it worked just fine. In 2015 I bought another 5th wheel trailer and at about the same time I saw the B&W companion on sale for about $750 at Amazon and my visa card was giving 5% back for buying online at Amazon so I went with that.
My conclusions (opinion):
I had the least bucking (push/pull) with my Lil Rocker, it was fairly light but I hated the bed rails.
I liked the B&W "system" because there are no bed rails but with the gooseneck adaptor there was quite a lot of bucking.
With the Companion 5th wheel adaptor, I still get some bucking, but better than the gooseneck adaptor. However, as I age, it gets harder and harder to get the Companion base out of the bed. 79 now and it's to the point where I am going to have to have a hoist of some kind or just leave the base in the bed.