Just a small note, you want more going out than going in because of course you will get negative pressure which isn't a problem in itself but you'll find that any smells will seep out which you don't want, its definately not a good idea. Also important to note that under the lights the temp will be on average about 10-15f more than the upper portion of your space. In small closets if you can't use a powerful extraction fan its probally a good idea to have intake at the bottom and possible passive intake as well. You could of course use a cool tube but they go hand in hand with extraction fans.