Following the basic instructions for a circular hat, I started with the magic ring, increased incrementally (per your formula) until I reached my circumference's diameter, then sc for 3" straight. At this point, I started increasing for the brim, increasing every eighth stitch for the brim's first row, sc even for the next row, increasing every ninth stitch on the next row, sc even & repeating the incremental increases until the last increase row had an increase every fourteenth stitch. I finished with a row of sc. I can wear the brim down or rolled-up. I think the non-increasing rows on the brim help to give it more shape.