For those who came in late, here's a couple of good articles by Stu Nettle discussing fins.
It is better to link to the articles. Easier reading, you can clink links in them, and see the comments.
www.swellnet.com/news/design-outline/2021/09/01/parting-the-water-part-1-fin-placement
www.swellnet.com/news/design-outline/2021/09/20/parting-the-water-part-2-fin-shape
