Actually, since you're talking about covering the ambient light sensor with a film that will prevent light from getting to the sensor, wouldn't it be correct to say you're trying to make it 'less sensitive' rather than 'more sensitive'?
I can say that the Light Dims worked well on my auto-dimming rear view mirror. I had always hated the fact that on fairly bright days the mirror wouldn't dim and that it was really slow to dim regardless of how bright the light coming through the rear window was. Placing one of the small, circular Light Dims dots on the forward-facing sensor on the mirror has fixed both issues completely. Making the mirror think that the ambient light levels are lower made the mirror stay darker overall and increased the speed of dimming when bright lights hit the rear-facing sensor.
2012 Red Candy 5-Door SEL 303A (built 2/27/12)
2012 Sonic Blue 5-Door SE Sport 203A (built 9/13/11)