Warning! There's still a mistake in the patterns even in the latest ones (I re-downloaded it today to be sure). Piece B, the 12 white triangleish pieces should have both sides the same length, if you measure it on the pattern it isn't symmetrical. And I don't think the curve is quite right either, it should follow 1/12th of a circle. I have re-drawn it & just carried on, I have cut out all my pieces (doing it by english paper piecing) but haven't sewn them together yet so I don't know if the rest are ok.
Of the two different length sides the longer side appears to be the right one as it matches up to the length of the sides of the red piece. So if you extend the short side (should both be 6.6cm) & then trace the curve in between from the big outer pieces they should work out ok. Will update once I've sewn them all together
Hope this helps. I'm seeing this project as a real voyage of discovery!