I know I know yield

For your dimensions I'd say a 600w would be perfect, as far as your other question like I said earlier, taller isn't necessarily going to be better in your setup. Either way your probably going to want to do some training. You could sog a bunch of them grow them tall and lollipop them so theres only the top cola, or just scrog or LST 1 or 2 plants keeping them relatively small so the light can penetrate through the foliage to the lower budsites. The problem is if you just grow out a 6' plant with your 400w HPS the light isn't going to penetrate enough to the lower budsites to make proper growth, so they will produce light fluffy buds if anything.

ok dude so I guess ill just do 2 smaller plants then thanks one more question when you take it out of 18/6 and put it in 12/12 and start the flowering time it doubles in size so if my plant is 2 feet it would be 4 and if it was 2 1/2 it would be 5 feet?

and oh do you know if any 600 hps bulb will fit in this http://cgi.ebay.com/400-watt-HPS-GROW-LIGHT-400w-High-Pressure-Sodium-Lamp_W0QQitemZ180136925188QQihZ008QQcategoryZ42225QQcmdZViewItem ? cause if so ill just put a 600 watt bulb in it

The figures of doubling in size apply pretty much only to normally grown plants, when you start talking about training and scrogging your plants your talking about turning what would be vertical growth into horizontal growth to accomodate your space. Look up some scrog and LST grow journals and you'll kind of understand better what I'm talking about .

yeah ok thanks and hey so its true about doubiling in size when growing noramlly vertically

So let me get this straight. You have more 16.5 sf and you're only going to do 2-3 plants. Bro, up the ante, you could fit way more plants. What you what is the center cola. Sure, some strains produce bitchin' multi-cola plants, but you could get so much more from that huge space. My closet growing space is only 2 feet deep by 5 by 6.5. You could grow at least 8 ladies in there.

well my closet is shped strange the celing slants down from like 6.5 to like 3.5 feet I could do like 3 plants at each like 5 feet tall so hey quick question hopefully its a simple question doesnt seem like there are too many simple answers on this site haha well the question is how tall should my plants be when I take them out of veggin time to switch them over the flowering like 2.5 feet I could do like just over 5 feet

bah no one answered his original question -- I dont know the answer but i will be growing in a somewhat simular situatioon soo nand was wondering what hte aprox yield would be.

haha I know right

The reason you wont find any answers about yield is that it really is a crapshoot and there are way too many variables. Theres no formula you can plug in and say this setup is going to grow so and so grams, because its a living plant not a machine and there are so many things that can go good or bad along its lifespan that it really just is a toss up until you do a few runs and get to know your own setup than you should be able to know what to expect from it and try to do better each time.

If you really want an approximate number I would say anywhere from Less than an Oz. to over a Pound.

ok but I gave all the factors that you would need to give an appropriate estimate

I get 8 lbs dried off of 4 1ooow hps lights every time