during weeks 2 and 3 i topped twice and got root rot due to: too high water level, too warm water temp, not enough oxygen. So I rinsed the roots, lowered and cooled the water, and set the timer to 18 hours instead of 20, added extra Hydroguard, and in two days its flourishing.
In my experience I've never seen any substantial gain by trimming in to flowering cycle. From what I've read, it's usually done in veg.
If it was me and space was an issue I'd lollipop a few bottom branches off to give the upper ones more space .