Once you get your canopy nice and flat I'd think you'd have a 4x2 filled around day 45 with ONLY ONE PLANT, give or take, of veg then I'd flip. You have enough head room to let it shoot upwards on the stretch.
Keep your light going great guns to keep nice tight growth. Nice good breeze helps here too. Continue to LST every day or two, a little bit at a time.
Your numbers are pretty much spot on but I see you're struggling with a bit low humidity but that's ok, just keep temps a fraction lower also to even out VPD. Keep increasing PPFD so your maybe around the 40 to 45 DLI at the flip which will be about all she can take. Nutes maybe around 1.5 to 1.9 EC.
When topping I let the plant go 2 to 3 nodes above where I will cut but always cut just under the higher node. Even then I still split them trying to keep them flat.
Your girls look picture perfect! Fertigate often. Run off around 20% twice a week.
You're on target for a perfect grow. I'd be supplementing calmag every second watering now around 50% recommended for that stage.