To save a few bucks on your energy bill you could try it with ~75% output and 24" like
@wietefras has recommended. I love my good old luxmeter to get an idea of the intensity at canopy level(12$, e3ay).
I would test the brightness across the surface at 36"(that's your target, because of plant response) then lower the heights to 24" and dimm the light untill you get the same readings. The plant response should be the same. Inside a tent with reflective walls the heights do not matter so much, but you have a lot of open space around the canopy where light gets lost.
You could even use a smartphone luxmeter app, because you need no true values for the matter.
I know, it's hard to believe that you get the same result with as little watts but it works.
50klx is often already too much and I can see signs of stress and slight magnesium deficits. Up to 40-45klx everything keeps nice and healthy and I see no signs of stress. As long as I use no CO² this will be my target brightness at canopy level. My light is a ⅔/⅓ mix of 3000°k CRI80 and 90, the conversion factor should be somewhere araound 67 or so. That means the 45klx are actually only 670, maybe 700μMol/s/m² in the best case!
Hmmm! Danmed, I thought I could use much more?!
Than I compared my results to HPS and what must I see? Around the same brightness point people start getting issues with bleaching ... also with HPS.
Since then I use the 40-45klx with very good results. Tops can grow closer and then show signs of stress again, but that affects only a few tops and has little influence on yield in the end.
Whether the lamp runs at 350w while hanging 28" above the canopy or whether it is only 240w and 12" distance does not make much difference. As long as I use my target intensity I still pull ~50g/sft.
To hang the light higher than necessary only produces diminishing returns and is wasted energy.