Also from what I read if you have a lot of sag to begin with then the set up is usually to raise the ball higher.
As you see my pic in my sig, that was my first attempt at mine and you see the truck and trailer are high in the middle.. I had to lower mine ..
Remember try to restore front to original height..
Lat thing so you can have piece of mind is take it to a cat scale when your done and follow the steps here.. This will tell you if you are good..
Post pics and what your final outcome is... Its nice to have happy ending to hear that it all worked out for you...
cat scale weight calculatorAlso post the #'s from your trucks door tags. front and rear gross axle weights. And post your tire max psi and lbs they can carry at this pressure. Then we can compare to your scale weight and see how your payload is doing...