Metal roofs and engine hoods will block GPS completely.

That's what I meant by hood. Damn.

I will look around for a good antenna. What I assume is the GPS antenna/receiver for OnStar is pretty cool. It is a 1"x1" device attached to the upper part of the windshield. Does anyone know where I can get one of those? I have seen class-mounted patch-style GPS antennas, but they are usually 2.5" diameter which may look a bit ugly.