You can still tweak as needed ( as long as stems are fairly pliable ) but there will be a point that you will not add anything more to the equation. After a week or so under flip , it begins to change gears and work on budsites building. That’s why a good Scrog DURING VEG fills the quadrants you are looking for. Some sativas try to get vertical at various points especially if your chosen light system has a more dominate light center over a more uniform spread.
Personally as soon as I notice any mid / lower stem sites going vertical , I just let them do their thing.
Sometimes the fringe corners will stretch as it wants light ( depending on your footprint ).
GL.