Usually, if I make a mistake, I fix it, and re-do the instructable. This time, I thought it would be good to show how to fix a problem area.
I cut the hole in the brim in an oblong shape, instead of a round shape. It really doesn't matter except that the hole is too big for the top part of the hat.
To fix this, I cut 2 moon-shaped pieces and sewed them to the sides of the inner circle, making the hold smaller.
After pinning this several times, it's best to pin one side, go directly across to the other side and then pin it. Work back and forth across the circle until it's all pinned.
Pinning it in order kept giving me gathered fabric at the end.