... what kinda plant is it going to be?
Marijuana, almost certainly. LOL J/K
I'm no expert but I don't believe that taking the cutting at that point would have anything to do with creating a hermie. Not for your cutting, anyway. Stress to the mother is another question.
I have taken a cutting from a mid stage flowering plant before. You have to be pretty patient with it. I didn't have much cloning under my belt at the time though, so it might have taken longer than necessary. It just seemed like it took a long time to root, maybe had to change modes first, you know? Also, I've read that taking cuttings from the lower part of the plant will likely root faster, as those parts have more of the cellular structure present that is needed for rooting.