My second post was inaccurate. Yes the payload is 3500 (and change) total weight. BUT the tc certification is for 2920 for a dry weight camper. The dealer stressed that point. This leaves about 750 lbs for 'stuff'. So the enhancement of the springs will add 2k lbs.
My BiL saiid the tire rating E is ok for the weight, ideally upgrade to F. He has to dumb it down for me.