Hey there,
I'm using 19.5's with approx 4500 # per tire rating. My camper has an unladen weight of 3250#, loaded-optioned at 4000#.
Those 19.5's, Rancho 9000's and air bags combine to create a sway free, stable platform for everything we do.
The "major" drawback is in the unloaded ride. Those 19.5s have serious sidewall stiffness(which is what I want when carrying my camper). That stiffness creates a rougher ride than stock. Using my truck throughout the year as a daily driver, I mount my old stock tires/ wheels to achieve a more "stock" ride.
See you out there,