As my Stand-Up-Paddle Board didn’t want to go straight because of the tiny fin it came with I decided to make one myself, as big as the fin-box could possibly take. Now it navigates like a truck… 🙂
3D-Printed core (6 parts) and then laminated with 3 layers of fiberglass and epoxy, and a lot of sanding.
If you want to build your own, here are the files.