That does seem like a fair rule. This is a part I need to replace as well, my story is aggravating and sort of predictable. My dogs practically live in the back of the Commander, they're normally with me when I go to work or just running errands. My weimaraner (normally a fairly chill dog as weimaraners go) likes to think that anything within a four vehicle radius is hers to protect so she typically lunges at the window/tailgate as the case may be.
Apparently on one of her tirades (sp) she broke one of the fins on the passenger side, possibly just knocked it out of whack but either way, it's not right anymore, I just haven't gotten around to popping it out.