The black edges were the result of my cropping some of the extra "ick" off of the sides of the gout image. The reason I then added the slight borders instead of expanding the image to the sides of the screen was because of TV overscan. I figured that, with the exception of computer monitors and some TVs, most televisions would make those bars invisible while losing a bit less off of the picture information off of the sides.

I started doing that with several of my custom discs after I noticed it being done on some anime DVDs, like Anchor Bay's U.S. release of The Castle of Cagliostro.