I've had incredible success with a 15 light 13 dark cycle. a 15% improvement over 12/12 with an identical clone (PPP) using the same res of water in a hydro setup. Only difference is I set up a dark tent over 2 and manually went to a 15/13 cycle. WHAT A HASSLE. Does anyone know of a 28 hour timer or other programmable timer that will handle cycles over 24 hrs?