I'm just learning this myself.
This is what I've come up with.
You need atleast 5 links at between the bar and the clamp. Ideally (in my situation) I've got 6 links. This is so there is no binding when you turn.
Also, Appearently, you want the trunion bars pretty level (parrallel to the trailer tongue).
Ideally you want the trailer level (front and back) and the truck to sit level when set up properly. You adjust the angle of the ball forward or backward to achieve the level trunion setup.
Now take this with a grain of salt with me. I'm still learning here too!!
This is a good read.
RV.Net Open Roads Forum: Towing: Travel Trailer Hitch Set-up Procedure