To me, it's more of how comfortable of a tow it is at whatever setting you have it set at.
Not what the scale says.. Sure, the scale weights tell you where you are at, weight wise, and a good thing to know, but when it comes down to it in the end, I just want a comfortable tow..
I played with the number of links on my rig the first year I towed the trailer.. This was back in 2002.. I got it dialed in to where I liked it near the end of 2003..
I did my adjustments with measurements more than weight.. Then I took it out and found what worked best actually towing it.
I settled on 3 links 'hanging', but I only have 9 links total..
This is my old truck, but even with the 13, I have it setup the same and it tows great.
Good luck!
Mitch