I do single stem lollypop method. I cut all but the top cola off when I put my girls into flowering. Top growth is never affected by trimming. It becomes a problem when you cut something from the top you run the risk of stunting the branches under it. If you cut everything under the very top you'll be safe. I do this so that I will optimize my plants with the space I have. By cutting all but the top (future) cola, you are allowing the plant to send all of its energy into developing that cola. I do my first trimming at day one flowering, then I come back 7 days later when I change out the reservoir and cut off any more branches that may have developed moving away from the main stem off. I check my plants one more time at day 14 and trim them once more if they need it (usually don't) just any branches again that may have started to stray away from the main conglomerate of cola development. When all is said and done, you will begin to see one mega cola developing. The fan leaves may start to overlap, but you don't run into a whole bunch of side branches blocking others. If leaves start to get too big, you don't necessarily have to cut them off, but rather just trim the tips of each finger on the leaf shorter to allow more light to other leaves. For example in regards to growing like this, my setup can hold about 20 plants sea of green... That means I have twenty top colas and several side branches all competing with each other for light. With the single stem, I no longer just have the 20 top colas, but I was able to double my pants to 40. I now have 40 plants single stem that all get adequate lighting and aren't competing for light. The 40 colas are all bigger than the 20 sea of green because of the way I trimmed. Secondly, when I was running the 20 plants... everything around the main cola was decent, but not as big as it could have been. Now all that space is consumed by a main cola instead of side branches. Does that make sense? Little high and trying to pack too much info in here I think. Anyway, I hope this helps... It definitely has helped me. Take care and good luck!