dimensions of the light should be on the site your buying it from or if your getting it at local store just call em up and ask for dimensions. i know my 400w aircooled hood fit nice and snug in a 32"x32" tent
2x2 only just at 62.5 wpsf anything over 70 i normally an issue id prefer a dr80
diminishing returns is around 50 wpsf
400w would be a waste in that area