I have seen these failures in all sorts of trucks, not just cat 50s, and almost always they are worse where the truck is used on rough unpaved surfaces, worse where the driver is a really big person, and worse where the truck is driven hard and fast over railroad tracks and potholes. as you noted, most often they last long enough to outlast the warranty period. I have also welded additional steel to the cover to 'harden up' the area that cracks, for those drivers. I am not sure why someone would expect the factory to make better something that normally outlasts the warranty, and I am not exactly sure why someone would single out a certain brand and series of units unless that was some sort of clue to the failure. isn't the design on the cushion tire LPG trucks cowling pretty much the same? doesn't the cushion have even more 'jarring' that causes that sort of metal fatigue in normal operation?