20% is as close as you can get to the factory tint. I'm friends with several guys that do tint and 20% is what ALL of them use to match factory tint. That's what's on my truck and it's a perfect match.
i have 35 on my front ones and i kinda wish i had gotten 30 like my friend got on his pathy, but it was free and thats all they would put on so im happy.
I do 20% on all my vehicles. I just take my chances, 35% is too light in my opinion. My wife's Altima is perfect with 20%. I may use some 35% on my windshield, but that's it.
One more thing to keep in mind. A lot of shops will make you pay cash and sign a form saying the vehicle is for show, only to keep themselves free of trouble from local law, and people that get a ticket and want to throw it back on the tint shop.
You can do limo on the factory tint. The shop will have to go over the factory tint with 20% and then 5% on the rest of the windows. I know a ton of people rocking their trucks like that.
I don't care to tint over factory tint because the glare is awful when you're trying to see out the back window. I had a truck that was platinum that was double limo and looking out the rear window was like looking into a mirror with the tint on top of factory tint.
