Sounds like the link #9 spec is set up per what the manual recommends for WDH hitches on the ford. With that said, for my set up, i run on link #8 with 4 1/2 links showing and it's perfect. I also run a 305 tire that has an XL load rating which provides for a stiffer sidewall. With every link you add, you are sending more weight to the front axle of the truck making the back end lighter. Try going the other way and see if that helps at all. I should also mention when I first bought the trailer, i had 1000lb bars and was getting a porpoising effect at times. I swapped them for the 1500lb bars and Link #8 to get it dialed in. Good luck.
