The pattern was tested in a group of testers.

Note: the hat is crocheted with two strands of yarn, the flower is crocheted with 1 strand of yarn. It is possible to crochet a flower with Worsted weight yarn, but it will be necessary a smaller number of rows.

Material and tool:
Main Color yarn: 150g of light blue DK weight yarn Angora Vita, 49% wool, 51% acrylic, 100 g/260m;
Contrasting Color yarn: 50g of blue yarn DK weight yarn Angora Vita, 49% wool, 51% acrylic, 100 g/260m;
hook size 4 mm(F), hook size 3 mm(D), hook size 5 mm(H);
decorative acrylic strasse of Colibri.

For this hat is better to use a soft yarn. You can use any DK weight yarn. You can use multiple strands of the yarns to make up a single strand of DK weight.

When I’m crocheting hat, I use a smaller hook than recommended for this yarn to hat was tight and it can be worn in the winter. here in Russia in the winter is very cold and the hat should not have holes that it is not blown by the wind.
If you use a larger diameter hook, hat after washing can stretch out and lose form. I use a table to define the type of yarn. Perhaps your yarn in America more thick and loose, but I think you just have to try and learn to crochet hat with a thin hook. Then the finished hat should necessarily be washed.
And I’m sure the result will make you happy.