I do it like the guy in the link I posted above. Take clones off mother plants, and root them in an aero cloner. I use 2-liter bottle hempy pots, so when the roots of the clones are long enough to reach the reservoir at the bottom of the 2-liter, I plant them and put them straight under 12/12. I can pack 50 2-liters in every 2 x 4 space, averaging 14-15 grams per 2-liter, so about 24 oz every 2 month harvest per 2 x 4 space. Granted, you have to find a strain that is conducive to growing single stocks with no side shoots and packing the buds along that mean stock. That doesn't mean the strain has to grow like that when you are growing full-sized plants, it just means that when you grow straight to 12/12 from clone, it has to do that.
The gram/watt standard measurement is flawed. You can't get an accurate assessment without the variable of TIME included. For instance, if somebody is vegging for 2 months, and then flowering for 2 months and comes up with a pound, while another guy in the same space is going straight to 12/12 with a bunch of clones in an SOG, and comes out with a pound, clearly the second grower is doing better.
Lights can't penetrate more than 18 to 24 in, so, in my opinion, there's no point in growing plants any taller than that. You know when you see pictures of plants being harvested, and all the leaves are trimmed off, and the bottom half of the plant is nothing but bare stem, and the top half is all bud? All of that empty stem represents wasted veg time.
SOG is the way to go. Not only does it maximize the yield of every harvest, but you get many more harvests in per year.