The following code makes the mandala in the image below. Notice that one petal of the mandala is shorter than all the others. I'm trying to get them all to be the same. It seems that this unwanted behavior is due to the FilledCurve's feature of closing all curves, even if they already close themselves. Does anyone see a way to prevent this from happening to produce a symmetric mandala? (Yes, I'm aware of the very cool resource function "RandomMandala", but I'm trying to roll my own for a special purpose.)
curve = BSplineCurve[{{0, 0}, {1, 1}, {3, -7}, {3, 1}, {0, 0}}];
rot = Table[RotationTransform[i*\[Pi]/15][curve], {i, 30}];
gr = Graphics[{EdgeForm[Black], FaceForm[Yellow],
FilledCurve[rot]}]

Thanks in advance.