The most i would put in a 4x4 would be 1kw, and even then you should have some height to play with or they WILL end up close to the bulb mid flower. Lol that dude's got 150/ft2 and only 5ft of height, -1ft for the hood,-3ft for the plants = 1ft from the bulb week 2 of flower.. Fucken hardcore lol