I reckon it's lower than that. The tint level on new mk7 GTI rear windows is a lot darker than the mk3 ever was and that is 65% (or 35% if you look it at the other way around).
(and you can spec 90% tint from the factory)
Interesting info thanks.
I'm of course thinking about tinting my car this year; she's completely black inside and out, and gets very hot in summer. Ideally I'd like the fronts bang on 70% (legal) so i can go considerably darker in the rear, say 50% so the contrast doesn't look stupid.
So for arguments sake, if the fronts are 90% i could add a 20% film to achieve the 70%.
I spoke to a somewhat popular company today who said all the glass would have to come out, which seems mental and not really a road i want to go down. They also don't have the light measuring gauge, which i'd assume would be a standard (if not least well handy) tool to have, if you're in that trade.