Did EITHER of you read his post? He vegged for 50 days. Its obvious that they will be over a foot tall, mygirls, and biggun your advice is just stupid. You tell him that 12 plants is too many? Why? Since he's vegging for 50 days, he'll have gigantic plants for sure. In fact, 50 day veg time is probably 2x too long.
But regardless, 12 plants is not too many for a single 1kW lamp, it's more than YOUR PREFERENCE.
And dont be a prick and insult the kid with 0.5g/watt. Any idiot with a light can get that.
So, original poster, here's the ACTUAL ANSWER to your question. Your yield from a single 1000w lamp is generally about 2 Lbs per harvest. Sometimes lower, 1.5 Lbs or sometimes higher, 2.25Lbs max for me. Each strain yields differently.
It isnt about how many plants you have under a light, its about making sure the top canopy of plants is non stop green for the entire square. That's it!
I wish I could -rep people for some of their stupid advice they post just for trying to get +rep wrongly.