I went to a local tinting company (Z-One Toledo OH), showed the guy my old car's tint and told him I wanted high quality: no bubbles, no peeling, etc and would not settle for medium quality. He showed me his car with tint %-ages and another workers car with different percentages (35%-5%).
Bottom line was he knew his sh** and made me comfortable. This was the day after I picked up the car from the dealer! I was reluctant to drop off a new car, but it was fine.
I have black interior and did 20% rear windows and 5% top of windshield (only 4 inches in MI - he went about 5.5 inches but looks great and I can't believe the police would care about that!) I HIGHLY recommend the 5% on the windshield. Blocks out the morning and evening sun big time. I would never own another car without 5% on the top windshield again.
20% from him was close to factory on minivans and trucks (about 22% based on manufacturer). I would love 'limo tint' all around but don't want to invite trouble from the law.
PS - I have a Maxx so there's a couple more windows than the G6 (same 3.9L w/3.69 so it's all good!) :glasses: