I know Reese says no less than 5 links, but I always ran mine with 4. I no longer have that rig and don't know where my CAT scale reading are, but that was the only way I could make it work. I had a 2009 Ford F-150 with the max tow options and a 30 foot Outback tow behind. I had the head tilted as far as it would go and I was using 1000 pound square bars. I drove it that way for over 2 years. Never pulled the bars off for backing and made some radical turns to get into some camp sites. Also pulled it through the Smoky Mountains. Of course, this doesn't mean everyone can get by with using 4 links. BTW, the dealer had the hitch so wrong it was ridiculous.
I was probably only off setting 100 pounds or so with their settings! Always check your set up according to the manufacturers instructions.