'Flat ' inside foils on side fins.

Side fins with inside foil have a greater effective toe in angle, so should have the toe in angle reduced slightlyAny side fin which doesn't have a sharp leading edge actually does have an inside foil even if most of the inside surface appears to be flat. Take a look at what happens to the leading edge if it is blunted or rounded off at all. . . the position of the leading edge moves, effectively creating a slight elementary foil on the inside even thouh most of the inside surface is flat.It is better to make a correct foil section on the inside as neither of the options shown below are ideal, the sharp leading edge creates turbulence and the rounded off edge with flat plane following it is not an efficient foil section