I went and read the old thread. I wish we had an answer from a RECEIVER manufacturer. I do know I contacted the receiver manufacturer on our 1999 Mercedes ML320. They clearly said THEIR receiver was rated for a 10" distance from ball to hitch pin. They said I needed to derate the receiver capacity if I used a longer drawbar. They said they thought that was pretty standard in the industry.
Sorry I do not still have the email, it was 14 years ago after all.
I know some think if I use a really long length drawbar I could tow a 10,000# trailer with a Pinto, but I'm not going to try it. To each his own.
One final point. It was said no receiver failures were reported here. Didn't I read a lot about GM receivers bending a year ago or so?