Every time I configure the compass successfully, I get the message "PreArm: Compass Offsets too high". The most recent values are X:-144, Y:-261, Z: 586. This seems to be causing an issue with the Motors. After dozens of tries of either "sudo ~/ardupilot/libraries/AP_HAL/examples/RCOutput/RCOutput.elf" or Ardupilot motor test/calibration have only succeeded twice. These problems seem to be interconnected in that in both cases I cannot get the motors to turn on.
There are at least a half dozen of us doing BBBMini builds in our local group, and so far no one has gotten past this point yet (although only a few of us are at the RCOutput test).