I think it's sort of like luck...if you really just shave the top bit off, maybe it'll split..maybe not. The whole "F*ck I Missed" thing is definitely not a misnomer. I think the further down that you fim the more luck you'll have because it gets closer and closer to just topping. I heard this very old school grower named Clackmas coot say topping and fiming aren't necessary, that tying down that top stem securely would produce similar results to topping without the delay recovery time. I don't know if this is true, but I know this man has a much greater knowledge of the cannabis plant than I ever will. Lol.
Since you've flipped to 12/12 no luck of trying again on this plant right? Or will you try another fim since its so early?