To put a plant in 12/12 that early is a waste of the plant.Traditionally you should wait until the plant was started alternating branches.If you top and pinch early youll never have clearly alternating branches, so a well established plant with enough veg growth to build on is necassary.Yes, a plant 4-6 wks old will double and even more than triple its size during flowering.All this is wasted if the plant hasnt developed a optimum of plant mass to establish a maximum of bud sites, before flowering.-usdi Agaluga