Most of us with experience towing know that the pin weight of a heavy fiver is what limits the size of fiver you can handle. There are some who feel the gvwr of the truck is the number that determines the payload a truck has. Others are comfortable staying within the rear axle weight rating. My Ford sRW can handle a 3200 lb pin and stay within the gvwr of the truck. Because I'm comfortable loading to the gross axle weight rating I will comfortably put up to 3750 lbs of pin weight on my truck..... It handles that very well. My truck is rated for a 21000 lb fifth wheel or gooseneck. A 21000 lb triple axle fiver might have a pin weight my truck could handle but a tandem axle of that weight would definitely overload the rear axle.