Putting foil on those box fan blades will help with light reflection as well as air circulation. The fan blades with foil are spinning and reflecting as the light shines, so it is almost like they are blowing light onto the fans. I've heard people say that foil on the blades increases yield up to 70%. I do it to all my fans.
The above post is fictional and should in no way be taken as truth.
If I were to grow cannabis, I would only do so to supply myself and my close friends. Doing this would take myself and my friends out of harms way by knowing the source of our cannabis, as well as take hundreds of thousands of dollars off the black market annually. It would also lower the demand of black market cannabis, and would ultimately help keep cannabis out of the hands of minors.