I used JiBB's modifications (love the idea of adding buttons to keep the ear warmers in place!), but since these were for my 2.5-year-old son, I cast on 50 sts instead of 58.

They fit very well, though if I were making them again, I might try CO 46 instead. (ETA: I tried the CO 46 approach with Felix's helmuffs, and it was a great fit with the XS Nutcase)