It seems to me that starting a seed on 12/12 does not mean that it's going to show sex or finish much faster than a plant thats on veg lighting and then switched 12/12. Plants have to mature. Wether it's on 12/12 or not. If you go 12/12 the plants going to grow a little slower and maybe in three or four weeks it will show sex. So I dont think your really gaining much with 12/12 as upposed to veg lighting for a couple of weeks then flower