Reccomended Autoflower Light Cycles?

Hello i was starting up a few autoflowers using a 400w metal h/hps. I was wondering how long i would want to leave the metalh on when they just sprout from the paper towel. I would also like to hear some suggestions for the rest of the cycle, 20/4 18/6 does it ever change throughout?

From what i understand bout autoflowering strains is just pick a cycle and stick with it. From what i have read most of them are grown on 20/4 cycle.

I have heard that keeping them on 18/6 was better, to give the plants a bit to rest, obviously not at first.

I am going to go 18/6 next grow. from my reading this is the way to go start to end. Good luck keep us posted.