The darkness of the tint won't matter much. Just get a quality ceramic tint on it, that will help the most. I did clear ceramic on mine and it helped every bit as much as the 20% ceramic I did on the roof of my Panamera. So if you like the factory level of tint, then just get clear ceramic all around (I even do my front windshield). I'm in S. Utah and it makes a massive difference when it's 110+ outside.