I attached the strip to the front halves of the shirt. I decided to do the same operation on the sleeves, but make gathers instead of tucks.
The overall result is a slightly more interesting black shirt with some lines in the front. I've blown out the black in the photo so you can see the details, in reality it's darker and the flaws are well hidden. :) I think the use of two black fabrics worked well, using different colors might be a bit silly, but who knows until I try it.