I was just debating on what % tint I wanted to go with before I saw your post.
As for the roof, although pricer, definitely go with 3M crystalline for the best heat "rejection" film. Unique tech.
Unlike other materials, even ceramic (although I'll be using ceramic tint for the sides and front) those materials will eventually absorb the heat (saturation) after some time. Ceramic is still superior to dyed tint and the ideal choice overall.
Since the top portion of the roof glass is tinted already, I may go with a lighter 50% film + assuming the stock tinted glass roof is ~35% so that you can still enjoy the sky view, while the rear window lower portion remains at 50% so that you can still see out of it ok, for what it's worth despite the rear being a bad blind spot as it is.
To calculate the actual VLT of the glass with film applied to it, you need to mutiply the VLT of the window tint applied by the VLT of the glass.
Ex. Applying a 50% film to the stock glass with a ~35% (assuming) tint to it, you would multiply
50% x 35% = (0.50×0.35)x100 =
17.5%.
So the stock glass and window tint would have a combined VLT of 17.5%, which is pretty dark actually, but may be proper for the roof in a hot climate...
I think I'll go with:
80% Windshield
20% Front sides
20% Rear sides
50% Rear Window = 17.5% Top Rear Roof Glass. -OR-
35% Rear Window = 12.25% Top Rear Roof Glass.
For some reference:
View attachment 825196
* As you may already know the tint % limit varies from State to State. Some jurisdictions are okay with going as dark as you want for the rears, but just the two fronts have to be at a certain %. I've had really dark >20% tint in all my cars for decades and never had an issue. - Some states have a limit of 24%, which means that IF the stock tinted factory glass is ~35%, you'd only be able to apply a 70% film on top of the stock 35% tinted glass = 24.5%. But yea... no one really cares.
Hope that helps.