Abstract: A fin mounting assembly having a fin box and a cover plate. The fin mounting assembly has a fin box with an upper end that is substantially closed and a lower end that is open with an outer edge. An elongated recess is disposed substantially central along a first axis of the fin box that is adapted to receive and secure a base of a fin. The upper end of the fin box has a flange with an outer border. The flange has a gradually increasing wall height curvature along the first axis, beginning adjacent to the outer edge of the flange and a greatest wall height curvature at a flange central portion. The flange also has a slot cover wall that extends up and away from the flange along the first axis and positioned over the elongated recess. The slot cover wall has an increasing width thickness beginning at the outer edge of the flange that increases in width and has a largest width at a slot cover central portion. A cover plate has an outer border and is adapted to be attached to the outer edge of the fin box.