I like to bend them like dominoes when i let them get too big. You would think there isnt enough space but once you do it the foliage is lower and like a roll of quarters going one way and then another, or like dominoes in a circle
Since you will get another stretch, you might want to clean the plants up and remove alot of the small branches that you know are gonna shoot out and be all crazy when you flower
you need the chamber 100% light proof. On top of this that looks like a sativa leaning plant so it may take at like 10 weeks some strains take 13 or even more
make sure if you are bending them , to water first. If it is fresher vegetation you can Pinch it then bend it down. the goal is to break the inner layer and leave the outer there and it will repair itself. The other way is less stressful to the plant, its just tying it down and each day tying it down more