From what I've grown, godiva is right on but be aware some strains, usually more Sativa-ish, can double or even triple in height during flower.
You would usually change to 12/12 lighting when the plant is half the size you want it to be. As they will double in height or a bit more depending on strain and growing conditions. If height is becoming a problem, you can top the plants. or you can tie the branches down.... bend the tops down, but don't break them, and they keep growing horozontially.