You are probably good to flip any time... you have 4-5 weeks of strong vege growth after flip. Those plants will easily fill in the gaps in that time frame. I've got more spacing and about to flip - put my money where my mouth is.
Figure they will 2x larger at least in 4-5 weeks and have 18-24" of vertical growth, assuming medium is properly constituted and your fertigations are dialed in well... Too many mounts will make the plant shorter, etc... There are a lot of variables here, so it's hard to give a one-size-fits-all assessment.
If you are new to growing and don't have all that stuff dialed in, you may want an extra week to be safe, but if it gets over-crowded, don't be afriad to prune off some growth in the first couple weeks of flower. You only need about 2.5-3 colas per sq ft... maybe 4 per sq ft for those phenos that only give golfball nugs and less densely populated bud sites. Stick to this greatly reduces maintaenance (pruning/defoliation needs) and reduces effort to trim with better bud to leaf ratios. More is not better...
Also, by sticking to this, there is no need for a 'defoliation' - a mass removal of leaves. So, same potential yield, less work, less wasted resources, less useless behaviours like defoliation etc etc... less wasted time... saves electricity.. the benefits are endless compared to a 'wild' canopy.
Figure you want the entire light footprint absorbing light - this is about the tops of the leaves where 99% of the photosynthesis takes place. Beyond that, you want 'enough' colas to distribute the yield... the more colas, the more distributed the yield will be. Big colas aren't necessarily better as they are more susceptible to pathogens. I'd suggest enough colas to have good-sized buds that are easy to trim... not necessarily the biggest buds possible. Be systematic.. you'll learn faster. Try more / try less with different grow cycles.. see what you like.
For the most part, if you capture all the light, asusming ~35-40 DLI at canopy level, then your yield is virtually inevitable and relative to genetics at that point, as long as you have 'enough' colas you'll get the weight your light provides.
As i improve my process, the goal is to reduce how much i have to prune off... I want to flip to 12/12 and do as minimal lollipopping as possible. Anything pruned off is wasted time and resources growing it. Some waste is inevitable - anything below my scrog level is destined to fail, so it has to be removed. Efficiency is beneficial in many ways.