[Brutus]

I can say I've beaten on my leaf springs before. Putting a pop-up slide-in camper in the bed of a '97 F150 will cause the bed to sag down to the bumper stops and just-about straighten out the stock leaf springs. With family in the truck, I was definitely over the payload limit. I put a set of Timbren overloads over the rear axle. Basically they're just a pair of solid rubber bushings that sit on over the axle, but off the bed when empty (so the suspension can soak up bumps when empty). As you load the bed, it sags down until the bed sits on the Timbrens. Kept the vehicle level and saved the suspension. Not having the low beams illuminate the night sky was an added bonus. Tires could easily handle the slightly extra load. Not sure about the axle, but never had any issues with it.