I know exactly what you are talking about. I was thinking that maybe getting new molding where the window meets the top of the car would fix it. The molding on mine is like formed to the window now, so If I got new molding I think it would make a better seal. PLUS, It seems like if the window isn't %100 up it is a better seal. Try putting your window all the way up and then letting it down a bout 1/8th-1/4th of an inch.
BTW, does anyones G2's windows rattle when they are down and you shut the door?