Several years ago I roofed my old house with the same shingles, and just cut up a standard shingle into thirds and angle cut the "upper half" of the shingle (image below) and laid them as normal. I found if I trimed the corners, they laid better. BTW when I shingled my house, I didn't have ready access to the matching ridge caps Now many stores sell them next to the bundles.
My roof was a straight run ranch with a 4/12 pitch. I don't think I would try it with anything steeper as they may not bend and lay flat over the ridge. Nor were they installed over a ridge vent.
They looked fine, I kept watch to see if the layers were separating over the ridge, I suspected they would so I kept an eye out. When I sold the house a couple of years ago...after 10 years it was fine.
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