On the original costume it's possible to see two seams, so I'm making a cape in three pieces.
I'm planning on using a wool broadcloth, so I don't want too much fabric at the neck, since it's going to be very bulky. I decided to use some kind of version of a circle cut cape, which gives you a lot of width at the hem, some really nice folds, but no gathering at the neck.
I didn't go for a full or semi-circle cape, I kept the outer sides of piece 1 and 3 on the selvage, so they are straight, just like the fold of piece two. I also cut all the angles at 45 degrees, since it's simple to measure even without tools.