It has taken me three goes at Porom by Jared Flood to get what I want; with the right yarn, correct needle size, successful marker movement in chart B, and, most important of all, the right amount of blocking I think I finally perfected it.
My first try was a complete failure, too much blocking ending up in a stretched out end result which I then, frustrated, completely felted in the washer. The second try was more successful, but I still blocked it slightly too much. Now it's finally the right size.
After more than ten years of knitting experience behind me, I'm finally starting to learn that I'm a loose knitter, and I had to go down a full millimeter in needle size to get my desired gauge, especially for the rim. I also learned not to stretch the rim while wet, so what I did was pull the hat over the blocking balloon while it was dry, and only then moisten the hat.
The yarn I used is Alpakka by Sandnes Garn.