NACA airfoils use two parabolas that are pieced together at the point of maximum camber for their mean camber line. A spline with a controlled vertex is a segment of a parabola that is not necessarily aligned with the x or y axis. It can be rotated. That generates a more smooth and continuously changing curve while not having the point of maximum camber occur at the midpoint between the leading and trailing edge. I'm not trying to say "oh you're wrong I'm so much smarter and better than you," I'm just explaining my reasoning behind this so you can tell me if it is at all valid. I have no idea if any of that actually has any positive effect on flight. It's just an idea with very little testing on my part, and with no further research to back it up.
Also, to clarify, I'm not mirroring that for the bottom. We're only putting skin on the top, so it can be lighter. I'm adding thickness to the rib, but not to the airfoil. What you see in that drawing is just the shape I was hoping the skin would achieve.