Hi, previous wearer here getting into wearing again.
I'm not the one with the most wearing experience, but FWIW:
You have dark hair, and only need a small piece. That's good news for you. Dark hair means slower color fading (my biggest headache), and smaller piece means less blending to worry about.

The main thing is to make it look so good, that it's basically natural hair. That's possible, but can take some time and effort. If the hair looks really good and you don't act nervous, then it shouldn't matter what someone might suspect or think. I just think that if you want to fool 100% of the people around you 100% of the time, well that's a lofty goal which could lead to paranoia. That's not to say that a toplace piece can look completely natural. When I wore toplace units, people complemented "my" hair like "it's so healthy and full looking" etc.. But there were some less successful days too, of course. There will be "bad hairdays"..

I'm going to be teacher myself starting from Autumn, and I'm going to wear a fullsize topper again. So I definately get your dilemma, but a small piece should be quite discreet I think. Just don't get too much density.

Anyways.. I say, go for it!