Hi again, I saw the HLG-600 but had some thoughts about it. The HLG-600 is recommended for a flowering footprint of 5 X 5. This is 4 QB 288 on a slate 5 which is 740mm X 390mm (that's about 2,7 ft x 1,3 ft). Correct me if i get the conversion wrong. Is this light getting enough PPFD in the corners ...

HLG sells everything you need to build the HLG-550 clone, minus the driver. Arrow electronics has the 480h-2100a for $129 plus free overnight shipping.

I've got mine up and running, and I'm very pleased with it. It's replaced all my COB units.