It does look good on you. I wouldn't worry too much about the line at the back. You see the same phenomenon on guys with their natural hair who have the same haircut, especially when the hair gets wet or they put their head back. It doesn't make it stand out as a hairpiece.

I would be a bit more concerned about the crown. That looks a bit odd. It doesn't give away that it's a piece, but it definitely draws attention to your hair which you probably don't want. Perhaps it's a deliberate fashion statement though?!