somebody...anybody....

Why the space limitations? You'll want more space later more than likely, and a double tier like that will be a pain to deal with, not to mention probably get a bit hot in there.

What type of room is it going into, house or apartment, and is that space your only option?

I would do 600's instead of 400's, unless you already have the 400's and are trying to save money.

Whats your plant # limit?

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its a house. unfortunatly, i have very few options due to little ones...two i can think of. first is the one i mentioned and the second is in the attic. the attic has a height of 5' 8. i have in my possesion 2 400w systems and 1 1000w air cooled system. originally the attic was my plan but we just don't have the funds for everything it would take to turn a bare attic w/ insulation into a fully functioning room at least until next tax season... my plant limit is 15... thanx for the help bro...much appriciated.

well, a 2x2 isn't much space and your going to have to keep plants really short and your going to have alot of heat issues..especially with 2 400's in that small space. The attic is still your best bet for success..sorry about your inconvienant situation.
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Go with the 1k in the attic. Plywood for the floor, panda stapled rafters to joists, tarp zipper and duct tape. CL for fans and anything else you need.

Ghetto style, but at least you can get some sort of return for your efforts. 400w in a 2'x2' will turn into a little oven.

go for the attic
a 400 in a 2x2 space is not the best plan

This all depends on what your trying to get. If you just need a little more than an oz a month then your 2x2 is gonna be fine. However, you do have a few issues to deal with. First, you have to see what your options are for cooling and bringing fresh air into your space. If you can blow hot air into your attic (or outside) and pull fresh air from another room in the house then your golden. The 400 might work but, like everyone has said it's gonna be REALLY hard to deal with the temps. You will have to air cool your reflector AND pull fresh air into the space. (pull air from outside the space through the reflector and push it back outside of the space. Then pull fresh air from outside the space, circulate it throughout your space, and then push it back outside your space) Your gonna have to move a shit ton of air.
IMO I think you should sell the 400's and the 1k and buy a 250 watt hps with a air cooled hood, and one of those little carbon filters and fan. Then you can have a very nice, efficient grow space that you could harvest perpetually in.
If you need more than 2-3 oz's at a time then your gonna have to do the attic... and that will end up being hot, dusty, and hard to work in. If you gotta do that, buy a 3x3 tent and use your 400w. Just my 2 cents. Good luck bro.

You should be able to get at least 4 oz's out of a 2x2x5 space and a 400w HPS. I've tried it actually got more than that in a old short DR60 tent so its very possible. Strain was not a heavy yielder either. I'm actually working with a closet now with a 400W HPS cool tube venting into the attic at 250CFM and it's working fine. I actually added 2 foot T5 bulbs to the top layer of the closet for a small sea of green also. Max temps I've seen is 75.