Carrier/rack problems of the 2000 Chevrolet Silverado 1500

Cracked frame between spring hangers: the framerails broke vertically from bottom flange to diagonal slot at or near neutral axis of both frame rails. The frame rail has large hole in bottom of rail horizontal flange of 'c' shape for accessing bed/box mounting bolts. Crack propagates from this hole to diagonal hole in the vertical web of 'c' shape rail. Overloading should cause the frame to fail from top down not bottom up. Due to the very thin oem material and torsion or twist induced into the frame by large offset from the shear center of the 'c' shape to loading center of the rear most spring hanger. This pickup has not been altered in any manner. Several complaints have been posted on the internet, with this same problem. Granted some of these are due to operating the vehicle outside design parameters and alterations such as lift kits and large tires. However the design appears not to even meet manufacturer's stated hauling and towing capabilities, which the aftermarket changes only exacerbates. The crack on my vehicle will only propagate further on my vehicle should I continue to use it within gm's ratings. This an issue could be life threating as near to total cracking could cause lose of vehicle control. Highway rutting while pulling a trailer causes some whip and this whip will worsen as the crack propagates upward.