Unfortunately I bought mine right before they came out with the ones with the dimmer switches so that's a bummer. But I got them going under just one of the lights from seed for about 2 weeks. From there I kicked the other one on for veg and had them at about 26" away from the plants. Very tight node spacing! The down side, I didn't veg them tall enough being that this was my first run with led lighting. I was worried about my light depth penetration. Next run I'll veg to about 16" tall before making my switch and see how that does for me. But with topping and lst they really bushed out under the lights. Like I said, tight node spacing which I'm definitely happy with. Next run I'll also be opening up the tent fully at 3'x4' with 3x sf2000 in it which will give me 50 watts per square foot. A little excessive but I don't think it will be with running co2 in there as well. Though, I don't know how often people run co2 with led lights. So I may be taking a gamble there. Let me know any questions or input you may have!