Plants space needs?

I have a hydro hut with the dimensions 3x4x8 and a 400w Hps bulb along with some other CFLs. I am wondering how much space is needed per plant and what the best setup (plant placement) with my huts dimensions and bulb?

1-2 sq. ft. per plant would be a good start, and, as far as placement goes, just fill that sucker up

EDIT: 1-2 sq. ft. per mature flowering plant. Obviously less for seedlings and mid-sized veggers.