I know this is an old post, but I figured I'd answer anyway
Steve Roylance had some stripes pop up that had the typical 2 dark stripes up near the head, but they formed into one single stripe down the middle of the back about 1/3 of the way down the body all the way to the tail. This is, in my opinion, an extreme version of a sunspot stripe. They're genetically 100% stripe, not motley. The sunspot spots just elongate and connect to each other to create the look of a single DARK colored/ saddle colored stripe.
A pinstripe motley is opposite - the center stripe being lighter in color (the ground color).