There are a lot of growers of Sativa's that highly recommend 11/13 for flowering to reduce the time needed to flower and reduce the stretch. The stretch is what I am concerned about as I usually start the seeds the first week of March and put them into flower first week or two of June. In the past the plants are about 24 in tall after manifolding to 8-16 cola sites before the stretch. My Indica dominate plants get to about 36-40 in and my last one filled half of my 4x6 grow box. So crowding is a concern to me as Sativa's have a lot more stretch to them. The stretch I had on a Gelato (a Sativa dominate) a couple of years ago took the plants to about 48 in. I am following and good luck ......