OK now I have one more question. I won't get to actually try it out till I get back from my trip, but this is how I set my box up so far.

W18"(1.5ft)xL18"(1.5ft)xH24"(2ft)

I have a 250W HPS bulb hanging horizontaly about an inch and a half from the top. I'm planning on putting this 4" computer fan that I hooked up to a 12v AC adapter to blow air UPWARDS while it sits right above the HPS bulb. And I also plan on putting a few tiny fans along the walls in the middle to basically spiral the air upward toward the bulb. Then near the flooring I plan to cut 2" holes on each wall for air to get in from (cool air is on the floor more often then higher up). I have the HPS bulb already hooked up (but without a cieling) and I tried turning it on to see if heat would be a problem even without the fans. Unfortunately it seemed like it was a little (not too much) hot for growing tomatoes. I liked that whole thing in the grow FAQs about making your own cooltube, but I don't really know where I'd find a tube to work with.

So basically I need to know of any more ideas that would eliminate heat from the bulb. Any help would be greatly appreciated. Thanks in advance.