Limo on the back three is no problem but that usually what people do on coupes, but since the windows on the front and back are pretty much almost the same size. You want to have a smooth transition. otherwise it will not look nice. If anything you might not want that much of a dramtic different in level of tint. You can do 15 on the back 3 and 20-25 on the front.
Heres a pic of a ilx with around 20% all around. It looks even.
Heres a pic of a ilx with around 20% all around. It looks even.

