Modifications:
Using fingering weight I got 8 sts per inch so I increased the top to 128 sts, knit to the specified 3 month length. I placed my second marker for ear flaps after the 77th stitch. Create ear flaps as directed - but make them end at 34 sts. I did the decreases for the brim area as directed, but just completed more of them.

The hat turned out great! it is big for the 3 month old I had in mind so I am going to give it to my 6 month old niece. Her head measures 17 inches in circumference which is exactly what my hat turned out to be - I’ll get some photos at Christmas of it being modeled and I’ll post hat shots as soon as it is done blocking.