Has anyone ever taken off their B&W hitch and found that you can take out the top bolt or broken it off while removing it? What would cause that to happen?
The hitch can shift around all it wants and that won't affect that hold-down bolt. That bolt only sets the downward pressure on the hitch to the bed before the U-bolts are tightened. IMO you actually could remove that bolt after you've tightened the U-bolts without any ill effects.