This is such a great pattern, the decreases are so lovely when done on a 16 stitch repeat.

It can be done on multiples of 16 + 4 or 8 but the initial decrease on 2 sections requires a little finagling to get the decreases on track - some of the stitches marked as the decrease stitches will end up falling between purl stitches rather than between knt stitches and so those must be reduced by performing an SSK with the right most pearl stitch and the knit stitch before it and an a K2tog with the second purl stitch and the knit stitch right behind it, then you will be set up for the regular style of decrease described in the pattern on the next decrease round. It does not match exactly as there will not be a column of two knit stitches running all the way down to the bottom of the hat, but it is not terribly noticeable and is the way I found to best to manage the decreases when needing to cast on less than an additional 16 stitches more.