Shaking my head at the futility of all this, I just added an inch to both the flounce and the underskirt and called it a day.
It was only much, much later that I finally found an English description of the pattern on the Farbenmix site that explained the two sets of pattern pieces were for the average size child and for children of more "stocky statures." If you want the skirt to be longer, you just need to make a bigger size. Ahhhh. I see.
Anyway, when all was said and done, I had this skirt, which turned out pretty well, I think!
Pattern: Farbenmix Zucka
The pattern is a little time consuming (all those pieces! All that topstitching!) but it goes together really easily. I will definitely be making more of these!
And in other news, I also made this:
Pattern: New Look 6936
This is such a great pattern. Totally brainless, a total of 3 pattern pieces, I think I only used about 1.5 yards of fabric, and start to finish it took about an hour. Love that!