I have 20% + 35% in the front, 5% on the sides and 2x 20% in the back and I dont have any problems with the heat. Im from Puerto Rico and the law here is no less than 35%. But Im a industrial tint installer for a few years and if you dont have problems with the law just put 35% all around, otherwise if your car have sunroof you can put 20% all around but be careful and if you see a cop just pull out the sunroof cover and you'll not have problems because the sunroof let enter an huge amount of light.