My payload is #1900 and I have #4050 rear axle rating.. Wouldn't want to tow a 5th wheel with it.. Just too dang heavy for what I'd want in a 5th wheel..
I've got 'XL' rated tires rated at #2833 @ 50 psi, but they are 20" tires, so maybe that's the difference?
Anyway, do what you need to do and if it works for you, that's all that matters... :)
Good luck!
Mitch