What is the color of your car?? I think the statement u made abt lukewarm under hot sun is very subjective......I had mine installed the UltraMax (given free by TCM).....and my car is still scorching hot under the hot sun....ok...i know i am asking for it....mine is a black latio with black interior.......unless we had different grade of ultramax installed....or....maybe mine is chong one by TCM??? haha.... 
My Latio colour is metallic red with black interior as you can see in my avatar.
Seriously, I find the UltraMax installed in my car to exceed my expectations. My previous ride is light metallic blue with beige interior and uses ThermalGuard. I experienced exactly as what you mentioned in your present car... interior still scorching hot even though slightly better than without solar film, always need to start the car, turn on the aircon full blast and wait for the car to cool down for a couple of minutes before entering the car.
Now, for my Latio with UltraMax, whenever I park my car outdoors (I work in construction site), even when I enter my car during lunchtime, the amount of heat is so little that I can sit on my seats immediately before turning on the aircon and the leather-wrapped steering wheel is only lukewarm to the touch.
Perhaps I got a different grade as you mentioned? Then I must thank my SE for it.
