If you are shooting for 8 oz. You will have to veg longer. My very first grow was 9 plants and got 4 oz. with a 1 month veg under 10-12 cfl's. I didn't train or use a hps, so right now you are going to be doing better. Starting from nothing sucks, you're going to be in a hurry. Slow down, I believe in scrog nets, with a 400 I would build a 3x3(about $20 for pvc, connectors, string and screws) add another $15($7 from harbor freight) for a pvc cutter or use what you have. Train you plants to fill that area up and then flower. 2 weeks before that take clones, get clones or start more seeds, so that when those are done, you already got 1.5-2 month vegged plants ready to go. If you are in a legal state, clones are easy to get. Flushing this way will be tricky if you go the scrog route.(you can't just pick them up and take them somewhere to flush) I already had a 2x2 flood and drain table, but I picked up what I think was a cement tray from lowes for $6 and a $2 fitting from the grow store that connects to a hose and pumped the water to a bucket to discard. Genetics does play a part in how much you will yield as well...