I have these vents for my defrost from **********:


I'm wondering how far away from the windshield they should be? I am thinking from the looks of them they will need to be about 1/2" away. If too close they just point at the windshield frame. What have you done and how well do they work? I'm using these for the original look but want them to function as well as possible in case I use a top in the future.
Thanks for any help
Rod