If you dont want to top em', switch to 12/12 before they hit 16" tall. If you aint runnin a 1000 watter at 10" or less, i'd flip em now, or top em down and flip when they hit 12". Ive come to the conclusion that one may as well go from 24/0 on clones and seedlings, to 18/6 for veg. then hit em...