Well, I did a "sort of" try out on the black border and the piano key border. It didn't work either. I tried it the piano keys on the bias and it looked better, but not exactly right.
I may try Ginger K's idea of cutting off the existing border, putting the black border first, and then adding back the panel border.
I'm going to play with the piano keys and see if I can't make them look less odd.
bkay