So this is just my two cents on this. By the way your nor going to mess this up
. The first set up branches growing out right above those little leaves that are dying off. That would be the first node, the branch that is going to grow up and produce buds. The one you have labeled first node is actually your second true node as pointed out by MYOB. You can cut right above that....anywhere between there and below where you have labeled second node. The way you have it drawn up now your showing the cut right above the third node. Everything below where you cut will grow like it is now the main shoot. UB recommends topping for 2 or 4 main colas....if you top above the second node like your picture showing you would end up having more main shoots but there becomes a tradeoff of more smaller bud sites vs one very large (no top one main cola) to 2 or 4 smaller colas. There is a sweet spot where the theory suggests topping for 2 or 4 main colas will out produce the one main cola but to many may decrease yield. All in all until you get down everything else you will prob yield close to the same regardless based on your other limiting factors. Top, Fim, lst, scrog to create many tops and a smaller bushier plant with an even canopy....recommended for limited verticle space, low light conditions, or just preference of style of growing. You could even top at the location on your plant and remove the bottom two branches closest to the perlite in you hempy bucket.
Saying all that know that topping typically creates a bushier plant....it looks like your grow space is very limited. It will be pretty tough to have 4 bushy plants in your limited space. If you planted from seed (not fem seed) then odds are not all will be female. Never know may just get one may get three ladies. If you do not top you might be able to do more of a SOG type grow and concentrate of 4 main colas.
What type of light do you have? Is this area in your picture for starting and vegging or is this space all you got? You can and should train your plants based on these factors, don't just think topping is going to equal more yield.
It is recommended to wait until your plants get about 5-6 nodes before topping. His plants do not look that tall or too mature to me? Don't worry about cutting your plant in half, those bottom shoots will start taking off. Anyway, before you go topping the top node or one just below go back and read the UB's topping thread again and get an understanding of what topping does and how it affects the plant. People end up topping in all different places and like I pointed out what are you trying to accomplish in your grow space?
