Right about......now.
Quote from Subcool: "I wait until there are 3 sets of real leaves (One leaflet, three leaflet, then 5 leaflet or some strains a 2nd 3 leaflet), leave those on, and take the top of the rest off. You will think I'm a dumbass, and it will take about 2 weeks for the plants to regenerate, but you will end up with 4 HUGE strong main colas."
He said something like that. Watch Weed Nerd episode 125 it's like a FAQ version of the episode.