I'm about to fit a wind deflector to my car this weekend. I don't have the silver covers with the holes in them and thought that I would have a go at drilling holes in the existing ones. It would help if someone could give me a distance from the bottom of the cover to the bottom of the guide. Also, is there a reason that there is a gap at the bottom of the deflector? would it be better if I fitted it further down closer to the trim behind the seats?