I have had tint done and re-done a few times on my black RAM.
Right now I am sitting on 5% on all the windows and 35% on the whole windshield with a double layer of 5% as a unibrow sun screen. It is dark enough that I have to dim all my dash lights to see at night. Would not go that dark again. 15% would be ideal but since the rear door windows are privacy glass from the factory your windows won't match front to back.
Do you want the front to match the rear?
Here is what mine looks like now.
Funny enough, I used to have 3 layers of 5% on this truck on all of the sides and a single 35% on the windshield. It was awesome in the bright days but I could not wear sunglasses ever and at night the windows had to be down. I got my first tint ticket a week after I had it redone to be lighter!
