Out of curiosity I looked up a couple of 2012 Big Country models and they run 15,000 - 15,500# GVWR which would put his pin around 3,000-3,300# and a 2012 3500HD SRW should be around 4,000# payload. Heck seen a couple 2500's hooked to loads like that. I disagree, but what do I know.
I agree he needs to run his rig over the scale to know what he's actually doing.
There are also some people who you will never convince that a dually, just might, be the right tool for the job. They can drive their truck and I'll drive mine.
Be safe and see you down the road :)