Hi again, we are about a week away from using it as a cloning chamber. I don't think that heating would be an issue with any light as long as there was proper ventilation. That being said, I wouldn't try to put a 400 or 600W hps into this chamber, unless you had venting directly from the light as seen on the light in the above pictures. but I would do fluorescents for better results.

420Paul the grow cabinet is actually not that small at all. Compared to some of the stuff I've seen on here where people are growing in small closets and even computer cases, I would consider this cab somewhat of a medium / large size. It measures approx. 4ft tall and is about 1.5ft deep and 3.5ft wide. I will keep you guys posted on how it works out later!