I didnt like the toxic smell the paint would've left behind. Not to mention the heat from the hps, only would have made it worse. As for adequit air flow, I have a 85cfm cpu cooling fan mounted at the top right corner of the cab, I also have an intake at the lower left front corner as well as an intake at the top center. As for cool air being drawn in, I have ducting hooked up to both of my intakes which are connected to a mini swamp cooler, which provides cool air and humidity. The temps inside the cab dont get hotter than 80 and humidity is always between 55-66%

The HPS is about 2-3 inches away from the top of the plants. I also have a small fan blowing over the tops of the plants to keep airflow moving across at all times. The only prob I see with my plants at this time is the lowest leaves have started to brown on the tips and fall off? Other than that they are doin awesome.

What do you think the brownig/yellowing is?