I waited till I had enough growth on the main stem and side stems so that when I tied it down it wouldn't be touching the growing medium. Till its long enough to reach the edges of your pot. Its easier that way and no damaged leaves. Then again I'm working with a pretty rapid growing monster strain. Quite a few people on here started LST when its at the stage you're on but there's examples of it going wrong like in Zain123's grow. He was unfortunate. I personally think its too early due to the fragility of a seedling or young plant. Think I started mine on day 16 and going on day 19 now its bushed out rather well and staying squat. Like a roided out midget [emoji23]