The cowl knit per pattern with no modifications is too big for a 12-yr-old boy. I actually fear it will be too big for his 40-something father, but he will be the lucky recipient anyway.
Therefore I began a second cowl, reducing the cast on by 20% and made it 1” shorter. I think this smaller cowl will fit my grandson well.
These are now a father/son gift!
If I were to make this cowl again for an adult, i think I would reduce the cast on by 20 stitches. I like the resulting rib using worsted and size 4 / 3.5mm needles. It feels good, and it will be warmer. I wouldn’t have thought of going down so many needle sizes when using a worsted weight yarn. It worked well!

The larger cowl took 2.18 skeins = 109 gr. = 214 yds
The small cowl took 1.62 skeins = 81 gr. = 159 yds