This was a ~2x2 box with a vertical 250w hps in the middle. honeywell fan under it blowing upwards. I just wrapped that wooden frame with pandafilm and clamped it on. Around the light, along the edge of the box was a trough made of vinyl gutters. I rigged it up like a flood & drain.
I only got away with it because it was the middle of winter. Otherwise it woulda gotten HOTTT in there. Also, it was too small for a filter, so my garage stank like the chronic. But crappy genetics and high temps aside, still got an ok yield for a 250w.
If you're in a box that small, you gotta find some way to aircool your HPS. Otherwise just get one of tthose 125/250w CFLs