800 PPFD before the flip is already plenty of light, so I wouldn't crank them the day you go 12/12. The plant is about to stretch, change hormone balance, and ask more from the roots, and a sudden light jump just makes the root zone and transpiration try to catch up all at once.
I'd leave it where it is for the first week of flower, then bump in small steps if the tops look happy. Something like 800 ppfd week 1, 850-900 week 2, then 900-1000 through weeks 3-6 is about as hard as I'd push without added CO2. On 12/12, 1000 ppfd is already around 43 DLI, so past that you need the whole room dialed or you just make stress instead of more bud.
At 48 inches and 50% you're probably getting a nice spread, which is better than blasting the tops from close range. Watch the leaves more than the knob: praying and steady color is fine, tacoing, bleaching, crisp tips, or the tops getting pale means back it off a bit.
