with a proper hood...A 1000watt HID has a 8x8 footprint
plants can be grown every 18", give or take. I would try and limit grow to 4x6 or 6x6 and guarantee yourself of good light coverage.

Be carefule of overcrowding...It will keep your light from penetrating to the lower foliage/buds and they will be immature...as well as rotating plants to allow light to play on all sides.

I recently saw 11 plants in flower under a 1000w HID
hope this helps.