With this group, JD, I watched for when they got sleepy and started to droop, and whittled the time down to 17/7.
The re-veg I kept under a 23w CFL light for almost a month by itself so I didn't burn or dry out the tiny starter leaves.
I left 4 full size fan leaves on the trunk to collect light, and a carbuncle formed about 3-inches above the level of the dirt with new growth.
As soon as a few small 1" leaves grew out I put it in the shade of the other plants and just let her be.
She caught up quick, though she's about half the size of the others.
I'm going to keep vegging her and a topped clone of a Black Dynamite so they'll be able to rotate in in another month or so.
I might even use the Extrema as a mother plant, since we are moving ahead of schedule now, and she is a bushy wench.
And, whodat: I'm to the point of kind of hoping that several of the flowers yet to show gender turn out to be male so I can pull them out of the line up to make more room.
I might end up vegging them out farther to make room for the rest of the known females (6 of 10 are for sure female, including the re-veg).