You could consider a clear ceramic coating on the windshield and a tint on the side windows, some users here reported it significantly reduced the solar loading and made the cabin much more comfortable.
Also, the cx-9 has two evaporator, one for the front and one for the rear. I wonder if shutting off the rear would change the output of the front (unlikely but might be worth a try.)
Also, the cx-9 has two evaporator, one for the front and one for the rear. I wonder if shutting off the rear would change the output of the front (unlikely but might be worth a try.)