10,000 GVWR for truck is so it stays in CLASS 2 weight rating
It is for MFG warranty & Vehicle registration issues
Payload is based on that GVWR so it is also arbitrary
None of the above are DOT legal issues
Axle/Tire Load Ratings ARE DOT Legal issues
Stay AT or Under the axle/tire ratings and good to go
15,000# 5vr GVWR using 22% pin weight ratio results in 3300# WET Pin weight
You will be at/close to RAWR.....depending on how much you load into 5th wheel
I tow based on DOT Legal limits.......Axle Rate/Tire Load Ratings.