H.A.F.
a.k.a. Rusty Nails
Spend $20 and get one of those lumen-meters if you haven't already. I am not going by any system except checking what the number is at the tops, and trying to keep it in a certain range. Trying to figure out what that number is for me, but starting low is working, except for longer flowering time. I'm bumping up the next plants a bit to see how that works.