My friend Gee’s bike is a Terry Symmetry, designed for (small) women, which poses challenges when mounting “normal size” components. The Bafang BBS02 speed sensor mount (with a reshaped nut) requires far more clearance between the chainstay and the wheel spokes than the Symmetry has:

The chainstay is nearly parallel to the spokes, so the sensor fits equally poorly anywhere its cable will allow.
The obvious solution is to reverse the mount and stick it to the outside of the chainstay, but it’s not mmmm symmetric: the other end is closed. Use a pull saw to cut off the closed end, stick the sensor post in the other way, and then it fits fine:

The sawed-off mount is visible from below:

It looks fine from the outside:

Mad props to Bafang for the LED showing when the magnet is properly positioned.