I’m currently flowering a Universal Kush plant under an
HLG 550 V2 RSpec, 3x3 tent. Puts off a lot of heat for that space, I’d recommend running at least a 6” inline exhaust and 4” inline intake to get an effective heat exchange.
Keep it on low and high (32”-40” or so) above seedlings until the third node pops/ or the plant is stretching excessively, then lower to 24” and half power until around the 5th node. I personally top plants at the 4th node, so when the 5th node is up I’m more confident it’s healthy enough to handle stress. So I crank the light power to 75% and watch for signs of stress.
At any rate, it’s a fantastic light and overkill for my 3x3 grow space, but it scales down in intensity so no issues there. Best purchase I’ve made in quite a while.