Hey there, just wanted to chime in here with a few things. Im not a regular here but hopefully I can help you out
Supercropping is mostly done during the vegetative stage to branches which are not the main colas. I honestly cringed when I saw your one plant had been topped 3 times. Supercropping is done so when the wound heals the stem will be stronger as well as the inner "pipeline" of nutrients being larger and thus hopefully, more efficient. It can be efficientlly utilized in a sog grow to push lower branches farther outwards. If done from an early enough stage on the main side branches, hormonally the plant will treat these as also the main cola - and develop many particularly large buds. It is particularly efficient supercropping side branches while fimming or topping the main cola, which will force the plant to find a new main cola, possibly resulting in many more than what one normally gets if many branches are topped at once - so not only can the fim give 4 new tops but the bottom 4 branches will be "tops." Done right you can have a plant with 8 tops that grow even at the canopy with no LST.
Anyways, I would really recommend against doing it during flowering. You will be starving the buds on top of "supercrop" for nutrients or water until the wound heals. Also you will notice the healed wounds are not appearing larger, as you would notice with a correct supercrop or even with a correct topping, you see a swelling at the joint with the stem. The absence of that tells me this is a weak-stemmed plant bending itself just enough in shape to transfer nutrients. Supercropping the same, main stem 3 times is pointless. It is really just choking the bud each time, until it heals again. Supercropping is mostly done at the base of the branch very near the stem, in order to facilitate a quick response.
What you need to do is simply tie it down. No harm to the plant, and the benefit is two-fold: it allows the canopy to remain even while allowing light to reach those lower budsites. Supercropping is really a vegetative technique, and can be done very efficiently alongside a sea of green or even scrog grows. The main idea here is forcing horiztontal growth, but in your situation with the light where it is - the plant is just going to keep bending up. Essentially the problem is that supercropping is done to "rebuild" the stem, it is not so much a training technique except for horizontal growth (which will not apply to a main stem without external factors such as LST).
Regarding stretching - in my opinion this goes back to the vegetative stage. Stretching is why I personally use a T5 fixture - it can be pushed right against the plants to force it down. Other than that, since you seem to like to use a lot of strains (read your last grow as well
); I would learn to utilize a LST method. It is very efficient, I personally tie and re-tie down my plants as needed until a week or so in flowering after they are done with that flowering stretching phase. After that it usually looks like a nice even blanket of bud, and the light can be put as close as possible and I do not have to worry about stray stretching plants. A screen of green is also an excellent method - you would be surprised what some cheap PVC and chicken wire can build you. Personally I would also recommend removing any new growth on the bottom 1/3 of the plant during late vegetative and early flowering - those baby buds waste resources being grown while not providing anything to the plant in the form of light energy or anything else. It is usually best to allow the plant to use it's available nutrients on the main colas getting direct light, as those will be the strongest and best buds in the end anyways.
Cheers