We sell a lot of those "Ranch Hitch Adapters" at the RV dealership I work at. They are a very fine product, very well made. We've never had a single issue with the actual hitch itself. The only complaint we get is that you will notice more 'bucking' motion while driving. Converting the 5th wheel into a gooseneck is like putting a great big cheater pipe onto the frame of the trailer, and the trailer frame will give a little. On an 8K trailer, you probably won't notice too much of this motion, but it will be there.
On much heavier trailers, I really don't recommend them, as the ride will be terrible, and it can lead to frame failure on the trailer due to metal fatigue.
I always recommend a regular 5th wheel hitch whenever possible, as hitching and unhitching will be much easier, and the trailer will tow smoother. Also, you'll put less stress on the landing gear of the trailer, since with a gooseneck you have to lift the trailer high enough to clear the ball, but with a 5th wheel hitch you just have to remove the weight from the truck enough to slide out from under it.
Casey
1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter