I've seen half the people suggest 20/4 and half the people suggest 18/6. I don't think it makes that much of a difference, but I do know that the people who invented the Easy Ryders (lowryder x ak47) suggest 20/4.
i know they say 20/4 and thats the schedule im on, i have been on it for a out a month, my question is will it screw things up if i go to an 18/6 schedule?
the whole concept of an auto flower is that they do not need to be on a specific light schedule to be able to produce flowers, i would believe that with this knowledge that switching to 18/6 wouldnt hurt your plants.