One more explanation for cracking bed is just truck build quality.
My friend bought Chevy 2500 pickup for his construction business.
The model was around 2010.
He installed lumber ruck and tool boxes on it, what within a year start making cracks on the bed.
Chevy denied warranty coverage as he not suppose to put tool boxes on contractor's vehicle :S
Friend kept using the truck with taillights hold by duct tape.
Meaning what did work years ago on some vehicles will not work today on different ones.
So now the question is
WHO HAS TORKLIFT TIE DOWNS AND CRACKS ON THE BED? ;)