Comment:
Since it's not a good idea to switch apical dominance during flower, it's better to throw a screen over your plants BEFORE switching to flower, and at the VERY latest, stop weaving new growth into the screen at the end of the stretch period- and I wouldn't even go THAT late. Once you have scrogged your canopy flat, which should be complete before you switch to 12/12, just let the buds grow up through the screen.