The car's in anyway.
Had a good chat with the boss and what's being done is:
40% front sides
35% rear sides
20% rear
He's done this on a few now and apparently it looks sweet.
The theory being that the front two will barely be noticably different but the front will still be better at 40% rather than 35%. Then the rear won't be obvious at all (as you won't be able to see the big contrast at the angle between the rear and sides).
And the 20% rear will help balance out the whole thing.
I trust them, they had a new beetle in (yet to be delivered to the new owner judging by all the packaging still on it!) and I'm guessing that the dealer had chosen them to tint it prior to delivery so if it's good enough for them, it's good enough for me. Don't really like the new Beetle but this black one was a beauty!