I have most of my music in FLAC on my large storage device, and would like to automatically re-encode it in Ogg Vorbis when copying it to my portable audio player (Sansa Fuze v2). I have set my Fuze to MTP mode and told Banshee to encode to Ogg Vorbis with quality 4 in the Device Properties dialog for the Fuze (I would use MSC mode, but don't have an encoding option in the device properties when I do that). However, when I copy music to the device, either by dragging it from the music library or by syncing a playlist, the full FLAC files are copied rather than transcoded and written as Oggs.

How can I get my Banshee setup re-encoding the audio?

If StackExchange supported bonus points, I'd give bonus points for a solution that only re-encoded music that was already losslessly encoded, but I don't think that's possible.