I hooked a 14k 5er to my coil sprung 2500 and it sat level. I regularly towed a 12k 5er with no issues. In fact, the 2014 2500 with coils sagged less with the same 5er than my 2007 3500 SRW did with Torklift Stableloads installed.
Here's a 12k 5er that's 37 feet long with 3 slides (one of which is over the pin) and all stock rear suspension...IIRC, the pin weight was right around 2000# when I weighed it.

HERE'S A VIDEO where I am raising the landing gear and letting the 5er's pin weight settle on the truck.