I went with a lux meter from amazon. See picture / model attached. Seems to work pretty well. I removed the reflectors and took some readings and I'm getting the results from the second picture attached. I'm currently between 50-60% on the POT / 18" above plants and everything looks extremely happy. Fixture puts off like zero heat with the driver out of the tent too. Working up light level slowly. 7 days into flower. Very happy with this build so far!