In the past, oil canning was not regarded as a defect and thus, not warranted. A poor installation will cause any roof to leak as the devil is in the details, particularly when it comes to roof penetrations and how well they're flashed + sealed.
Get striated or minor ribs to fight oil canning. Oil canning is guaranteed on flat pan metals. If the install is done to factory spec you'll have a lifetime roof. Also you can attach solar panels to the ribs with no roof penetrations!
