Hmmm. I am trying to picture all of this in my head. I am assuming your shower stall has an opening at the top?

I can't believe it is so hot in the tent with a 250w light. Is the ballast a digital one?

I have a DR120 with an air-cooled 600w light (remote ballast) with one ~250cfm can fan, and the temps stay about 7 degrees above room temperature.