Hello its andrew potter again is it good to flower...

Do you provide CO2? PPFD supplied to plants? With this info you can use a DLI chart to see if it is worth it in your context. If you need help converting umol/s (from light specs) to ppfd, you simply use the ratio of 1m^2 / your area^2 multiplied by umol/s off specifications. Once you convert your light's umol/s to ppfd (which is a per m^2 value of photons/s), you can compare DLI values in a DLI chart for 18-24 hours of light and determine if you are giving too much... If not, it'll probably be a benefit. (darkness being a benefit too and different break-even analysis i don't know with as much precision as this -- meaning, don't give 24h as you already seem to avoid in the question) DLI chart on google image search will give options. I have one linked in my profile and it's just a picture in a grow diary right here on this site - i.e. safe to use. upto ~45 DLI without CO2 and upto 65 with 1300-1400ppm or so of CO2 or whatever that takes, lol. Now, all tha tmath is using optimal photons from spec sheet.. this will be less in reality due to walls absorbing things and .9^x per bounce diminished, if not. However, 45 is likely too high, so it'll be beneficial to be a tad lower relative to all other factors invovled -- including our care for it. A bit of trial and error is needed, if you push the boundaries of either -- with CO2 or without it added to normal atmospheric levels as long as your over 21-22DLI, don't feel bad if not pushing "45" or "65". That's enough to flower marijuana.

Unless dealing with autos, photoperiod plants will only flower consistently with 12 hours on and off. If doing autos in my experience I've had s little better results with 20/4. Happy growing and stay lit fam