In NC, 35% is the limit, so rather than attract more attention from the troopers, I decided to stay there. Remember, the glass already has some tint as it is, so adding a 35% tint film over the already slightly tinted glass is really all you should need.
On my Astro Black '08 MCS, I did 35% all around (not front), and I have no sunroof. Black interior stays cool (white roof and no sunroof helps), and I can see just fine.
In some states you pay an additional fee when you have your car inspected as they meter the glass to make sure you are legal.
