He means that due to the stress of the bow pulling on the corner seams, it will cause the top of the seams at the corners to crack and then a leak will begin. Now, in my experience, once the top of a seam cracks it is only a matter of time until the entire seam splits open, or slowly cracks and gets worse. I hate to tell you that but it is, in my experience, what will happen IF the corner seams crack. There is no guarantee that they ever will. But, it is a dangerous game of what if.