I admit, I didn't read every response, but I'm answering the first couple things I saw.
That is just way too much light. You are gonna be killing your air conditioner. Good thing it's winter time. I had to remove my plants from my first tent because they were growing into the lights. That was with ONE plant in a 2x3x5 tent and ONE 250 watt HPS. I took the tent out of the closet and turned it into a proper grow space. I filled it (3x4) on the first try with one plant and two 200 watt blurple led's. Third go around, I have a whole new room now, with one 600 watt HPS, and one 200 watt HPS. It is more than enough to cover the 4x6 space. When they get big, I may need to add some support lights on the outsides of the 200 watt light. Other than that though, it's a waste of power and money. The plant has light saturation point, where you can add as much as you want and the plant will not take it up.
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Pmax = Maximun Photosynthesis potential. The green lines going up straight represent sunlight. As you can see plants evolved to take only what they need, the rest is not absorbed and passes through the plant or is reflected. This also causes excess leaf temperatures, leading to problems.
Yes, the real question is coverage and penetration. So if you grow in hydro? 1 gallon pots, or ten gallon pots? The answer is the same, as many as will fit in the space at maturity. without crowding each other too much, or shading each other. Light coverage is less about wattage and more about coverage.
The only benefit I can think of for multiple lights per plant is getting that light from multiple angles. Especially with LED's which naturally have less penetration.
