You don't think 16/12 will work? I know it's not a 24 hour day, but do the plants really know how long a day is. I got this timer that goes by the day and I could set it up for almost any time schedule. If you think it's a waist of my time though I won't bother. My room gets to hot for HPS, and my ventalation sucks, I got to cut some corners if you know what I mean.