I bought the weld on hooks but never used them I just got a receiver tube welded to a piece of angle iron and bolted it on, the reason I bolted it on was because I wasn't sure how it would work out, that was three years ago before every one started doing it (not saying I was the first) so I hadn't heard any positive feed back.
Now I would just weld it on because there is no reason to remove it, it's really the most simple useful thing you can do, jockeying trailers, hooking ropes, cables or chains, even made a gin pole.
I don't think you need the hooks once you have the receiver, with the hooks on the sides you have to use both to get an even load, with the center mounted attachment you have that solved, at least in my case I have never once wished I had the welded hooks, but couldn't live without the receiver tube.
JB,