Swap the Car.
I, too, got a grey tint with a high metallic content myself. I did 30 all around. (I am not a big fan of having two-three tones of tints on m car.) While some people like it darker (20- 25 or even lower), I found 30-35 to be perfect. Because the interior of the STi is relatively dark and the windows already have some light green tint, the 30 all around make the windows look quite dark, actually.
The tint film characteristics, according to the FTI's Diamond Metallic Film spec sheet indicates: heat rejection 48.7%, glare reduction 62.9% and UV protection 99.0%. Based on numbers alone, it seems that metallic tints not only last longer (or.. at least a longer warranty typically) but also have better heat / glare characteristics.
It even came with life-time warranty (i.e. as long as I own the car), by the way, which can be leveraged even if I damaged it myself intentionally, apparently... (according to the store manager)
I did this at a local Tint King (I know, a shabby name, but they did a terrific job). It took 2 hours and 15 minutes or so. I thought it was done very fast as most others quoted 3-4 hours for the job. They asked me to return in a few days for inspection & refinement (if necessary).
I was looking for a light blue tint (a la Mercedes AMG) initially, but I noticed that (1) it was impossible to find the same light tint apart from rather ricey bright blue tints; (2) the blue tints I found came with no metallic content and minimal warranty if at all.
Hope this helps.