I made the 45cm size for 6-12 months. I followed the pattern as written but added some sleeve decreases every 10th row 3 times. The decreases were: 3 stitches before the underarm marker SSK, K1, SM, K1, K2TOG. I used Jeny’s surprisingly stretchy bindoff in pattern for the ribbed bind off.
This is a fun and easy pattern to make with very satisfying results!