Interesting idea for the top. I have been playing with this idea for quite awhile, the "perfect" top. I agree, with a mister running, holes speed up evaporation, in my experience.
I believe also that until the plasitic starts to cloud, the lighting remains peak, assuming ballast is good, tubes are new, etc. There are many factors to consider when looking lighting.
The best system I found is one that helps to maintain set levels of humidity and temperatures while being able to provide healthy lighting for the plants. Without a spectrum light analyser or light meter, to test the existing lighting, we have to watch our plants and let them tell us what they need.