Yesterday I assembled 4 boards with my neighbor, one of which he flew on today with success (other then the 10V regulator whining at low battery).

While finishing up the build I got a chance to probe the Vbatt rail and LC filter rail while he ramped the motors up and down without props. The result:

Green is the filtered rail and damn near silent (would be even quiter if the oscilloscope probe reached the analog ground. Yellow is Vbat. AC couple of course. Another design tested out and as good as expected. :)

I wonder if installing the low ESR tantalum capacitors on the Vbat rail would improve the situation? Unfortunately they are way too expensive to do in production. At least people have an option and there is already a home for four of them on the board.