Very easy to follow and good illustrations drawing the pattern. I am assuming since you didn't add any ease to your measurements that the fabric is stretchy. Thank you for sharing your knowledge!
Underbutt is about 7 to 8 inches above the knee but I used 7 inches. For the length of the skirt, I'll advice you re- watch the video so as not to be confused cos I went with a different length along the line.
