I've made these before and my understanding was that the middle trapezoid is *not* supposed to be flipped. When all the long sides are on the bottom, it makes the hem wider than the top, which you want so it doesn't flap open as you walk. It also makes the skirt curve, which helps it get around the body neatly.
I'm glad I got to your message, because thats what I thought, but thought I'd got it wrong. I'll give it a go your way, Ta