I leveled my 2005 GMC 2500 with a 2" lift kit. I have a 6000lb unloaded trailer. I'm getting some reared sag when hitched up. I raised my L bracket but it did not take all the sag away. I'm lookin...
There are other options. Timbrens, SumoSprings, RAS. All will lessen sag, and no air lines needed, mostly install and forget. You can adjust the RAS to bring back a little unloaded rake and set it for various levels of weight help.