I've recut the dress again to make both the dress length variation via v-coordinate-driven transparency and vertically striped patterns work. My trick for getting the UVs I want in MD is to arrange the pattern pieces accordingly in the 2d window and then to make MD copy that layout into the UVs.

By the way, the thin pieces are hems. Getting the hems to fold in correctly in MD can be fiddly, so making them separate pieces is usually easier.

-- I'm not mad at you, just Westphalian.