Update: I contacted V-Kool directly, and they aren't doing automotive tinting at this time in Florida despite the option on their website (well, I mean they don't have any dealers doing cars right now)
Anyway, I think I'll be looking into the Huper Optik ceramic, since it seems like my only option at this point. I want to keep a transmittance level above 70% on the windshield... thing is, a lot of ceramic tints I see only block about 45-55% of IR. This is much better than the 15% of regular tint (at dark light transmittance levels, too), but still, I'd like to have almost complete elimination of IR heat.
Oh and also (and the poster above me, thanks, you're right), it's not really "tinting" on certain models of MB... it's an "expensive and difficult to produce and apply factory glazing" that they use. A helpful local tinter explained that to me.
On the hunt again for some heat relief... thanks for the help guys, please feel free to give more advice/info if possible!