Just a quick note, I'm up and running with dual 24/7 over a 60P. Running with pressurized CO2 ... my old controller broke so I'm just winging it until the new one gets here -- but I'm at around a kH of 2.5 with a pH of 6.3. In other words, should be pretty well set up for high light as I'm used to.
I ended up going with a staggered light cycle where the first light is running at the clock time in the 24/7 cycle and the second light is 45 minutes behind. Figured I'd try it like this for a bit to extend the higher PAR period since it seems rather short.
Coming from the metal halide and T5HO world, I really am enjoying the color variations, intensity variations and most of all the lack of a ridiculous amount of heat and energy use. It remains to be seen if I get good growth; I intend to stick with this cycle at least long enough to see where things are heading. If it doesn't look good after a few weeks I'll probably chalk it up to experience and just go with a typical 7-8 hour timer cycle on max.