Did brim part of the cast on as a crochet cast on, with the yarn doubled, then continue on with the long tail cast on for the rest of the stitches. I put the paired stitches on their individual needles at the start, to avoid twisting the bloody cast on, and also to have them already separated for the top & bottom of the brim.

Kept the second part of the brim cast-on on a short cable with stops on either end while knitting the first part.

Added extra knit row to the bottom of the brim, before casting off, to help it stand out more.

Crown:
Adjusted placement of stitches to center the front cable, and put the two blocks of P5 on either side of the middle-back cable. Removed the R1 decreases, since there was ALREADY 70 stitches! (And the number of knit & purl sets would not fit otherwise.)

R1 of the crown: Slipped the first 3 stitches, moved the ‘start-of-round’ marker to here.

R 22: Need to reduce by 10 stitches, in purl sets only.
So, for the P6s, P2TogTBL, P2, P2Tog; for the 1st P5; P2TogTBL, P3. 2nd P5; P3, P2Tog,
In spite of the different notation, it appears that the
cable sets are the same in this round.
(The notation is reversed, but the pics & chart indicate
no change.)

R 28 - the written instructions have the cable reversed. I followed the chart instead: P, 1B1, 1F1, P

Didn’t bother with the optional crochet button.

Used a clear plastic (the kind often used as ‘windows’ in tents and collapsible campers,) as the stiffening for the bill.