Two 260w kits is almost the same like a HLG550 kit. An HLG-240 with two boards in parallel tooks up to 285w from the wall with two kits it's at least ~520w net. That's ~32w/sft; enough for my taste...
The boards are probably not identical also if they claim so. If its LM301b it's probably not the same flux and voltage binning so do not expect the same brightness and wattage. PCB's are also only 1 or 2oz copper boards instead 4oz boards. Also, do not mix them in parallel with the org. Qboards. They have different input voltage and could be damaged.
But if you agree with all this things there is nothing left spreaking against this fake boards. Also the brightness difference can be reduced if you hang them 1 or 2" closer to the tops.
A few guys here use these boards with great results.
@Moflow for instance has a few 3x 1ft boards with 800 LM561c and his garden looks like a paradise AND he also use original Qboards in the same garden, btw..