Above is a link to my current journal, if you want to have a look dude....my apologies in advance bcoz there are no bookmarks and it's nearly 100 pages long hehe but I am sure there is a pic by pic of what I do when I top somewhere lol...and in answer to your question....I cannot tell you the
right time to top...as I don't believe anyone knows, bcoz what we are doing to the plant is unnatural....buuut I can tell you when I top
...so, what I usually do is top at the 3rd node, but which I mean I keep the 3rd node and cut off the 4th node....usually, I take away the 1st and 2nd nodes as well, at the same time, which pretty much gets all the HST done in one go...also in your pic, I noticed you left some stem below where you cut the main stem..
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....really good move there bcoz it adds some strength to the node just below... sometimes, if you cut close to the node and then tie them down....bcoz you are pulling away from a single point, it can split the stem in two...which you don't want haha...I hope this has been of some help to you dude, if you need anything else dude....just tag me in and I will try to help as much as poss...happy growing