I don't know which grow your basing this off, as I haven't seen much activity from him lately. Maybe he moved into a different forum category
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I do recall the one he had a few months ago, which I followed and learned A BUNCH from. The only issue I now see with that setup of his was that he used no reflectors or lenses, so the Vero 18 COBs were emitting at the standard 120 degrees (not ideal for growing in my book), and the COBs were many feet away from the canopies. I don't believe he was running his COBs very hard either, like 1400mA I wanna guess? (So each COB was emitting ~38W)
Anyways, the whole watts per square feet/yard/meter deal is fine and dandy but the grower has to take into account that we're living in a three dimensional world, where volume, not area, takes prominent precedence among the things that what we do. That being said, you could have 100W/ft.^2 but if the light(s) is/are 4 feet above canopy, your going to have poor results - atleast in his scenario.
I could be off my rocker with this claim but I'm just using my newly found experience with the VERO 18 series. Feel free to correct me or add to the conversation if you like.