I just purchased a 22k chassis, triple slide (Tiffin 34TGA). I took it to a CAT scale on my test drive. 19,080 completely unloaded. Do the same. I told the dealership my plans and they were fine with it.
I've been weighing and logging EVERY single item that we load into it. I think I have it all and have 550 pounds left for groceries. It works, but just. Once the kids leave, I think we won't have to watch as close, as that will clear up 6-700 pounds.
I believe you've gotten good advice above! Critical advice.