cardboard box. thats great!!!! ghetto grow 101. make a "heat shield" or reflector out of foil for bulb to direct heat downward, or away from cardboard ceiling.
I'm only a noob here, it's fairly simple though. With the fan at the top of your box it will draw cool air through the hole in the bottom. If you put the holes at opposite sides it will draw cool air over your plant too.
looks great!! just make sure you are PULLING air OUT of box with fan(not pushing air in.) As fan sucks air out of box, cool air will suck in bottom. Pix looked like fan might be blowing INTO box. If not sorry. IF SO-try reversing flow like i said. Temp should drop a bit more.
the fan is exhausting the hot air from the box. and the temp keeps around 26.5 so i think it's ok for now..
i'll try and find some small fan to put inside for circulation..