Since fin surface area is, at best, an arbitrary number, I think it would hard to apply the differences to the non-conventional fin shapes. Length x Depth gives us a pretty standard way to determine how much fin you like in the water, but it's not actual area. Assuming that someone who likes a lot of fin overall may need even more if it's a "pointy shape" is fair, but I can't imagine a way to accurately figure out how much.
(tldr - I don't math enough to figure it out)