I saw the hlg 550 in action.
The plants look well.
He sezs he'll let you know in 9 weeks lol
4 plants in hydro with a 100 litre res.
4 ft long x 42 inches wide x 7ft tall area.
He normally uses 2 x 600s in there.
The hlg is running at around 250 watts and the 660 hps is running at, we'll, 660 watts.
Lights are about 2ft away.
I warned him against putting it too close too soon
He is well pleased with it and will be getting one in a couple of weeks, maybe 2 of them.
I've to go over on weds to clean out the bases of the plants for him so I'll see if he'll allow me to take a couple of pics...