Shell stich baby hat

Babyhat
I got an idea ... a baby hat, not because I know if he will need in the second half of August, but it may be cold, then...
If nothing else, a friend will have her baby at the end of November and then it can definitely be nice with a hat.
This is 35 cm in girth, but can be used up to 37 cm in head size.
Pattern:
[1] 12 dc of the magic ring (12 dc)
[2], 2 ch, 2 dc in each stich (24 dc)
[3] ch 2, increase 1 dc in every second stitch (36 dc )
[4] ch 2, increase 1 dc in every 3rd stitch (48 dc)
[5] ch 2, increase 1 dc in every 4th stitch (60 dc)
[6] ch 2, increase 1 dc in every 5th stich (72 dc)
[7-13] 1 ch, *skip 2 stiches, make 5 dc in 3rd stich, skip 2 stitches, make 1 sc in 3rd st*You may adjust the final shellstich so you get five dc in the previous round first sc. Then, continue around, 1 sc in top of the previous round "shell" and five dc in the valley between the two shells on the previous round.[14-15] 1 ch, 1 sc in each stitch.
This I have used:Yarn (24 stitches, 32 rounds)Crochet hook 3.5 mm