I started making one of these hats yesterday and was frustrated that the cast on number is not divisible by 4, which screws up the ribbing pattern.
So note to others who may have this in their to-do basket: If you want the 2x2 ribbing to work out nicely, cast on either 80 or 76 (not 78 per instructions). Then adjust accordingly when (or before) you get to the decrease section.
My hat is looking good so far. I hope to post a picture soon.