Just wanted to add to those mentioning tinting over an already tinted piece - Most factory "tinted" glass is really privacy/dyed glass that has no additional heat/UV reflection properties, it just makes the glass darker so it isn't a fish bowl. Which is why most, even SUV owners that normally have rear windows tinted from the factory, have ceramic put over them.
To add to the debate, local shop around here recommended if we tinted the sunroof to leave it cracked and not sealed when parked in the sun as they've seen a lot of sunroofs pop due to tinting and being closed. There are also some Vortex posts on people having their pano roof shatter while driving and most of them mention being tinted over the privacy tint. Unless you drive with the cover open but the glass closed where radiant heat would be a big issue I think you'd be fine not tinting.
I went Llumar IRX nano ceramic 15 around the back and 30 on the front with Air 80 on the windshield. Tin roof for me, but I can leave it parked in the direct sun in the summer and jump in and not be immediately sweating. It's warm, but not holy shit instant sweat dripping hot like it normally is.