After some good experimentation, I have found it best to go with no more than 5 plants per 600. That being 4 on the corners one in the middle on a 4x4 tray. On good strains, (not sacraficing quality) you should be able to pull down 3oz/plant, maybe even four if pruned and tied precisely to a canopy. This should give you a decent yield of 15ozs-20oz/600watt.