Marty,
My first thought would be how well does it work? Not too worried about the grounding, etc, if it performs like it normally would. If you feel like it, try grounding the carport. See if it makes a noticable difference. If not, don't worry about it. The carport metal roof will have as much "ground" as a car, if not more! You could always try insulating the metal roof from ground to simulate tires on the car. (PLEASE take pictures if you do!)
Interference with the neighbors? Eh, could be, then again, probably not. 'Nuther one of those try it and see thingys. There are so many different reasons/causes for interference that spending too much worry about it before hand is just wasted worry. You could always move the antenna to the center, rather than one corner. Or change corners to see how 'directional' it is? Or better yet, just tell the neighbor to move... works for me.
Good luck.
- 'Doc
In all seriousness, it sounds as if it's working as well as can be expected.
That 'move' thingy works for me cuz I'm sort of old enough, know how to drool just right, and scratch at odd times that 'they' just don't want any more to do with me than they have to, you know? Hey! It works at 'Wal-Mart' checkout stations too.
