Default [Q] Preserving Rdio offline songs when flashing ROM

I love Rdio, but I frequently flash custom ROMs on my phone. I've yet to figure out a way to avoid having to redownload all my Rdio offline songs after flashing a new ROM even if I still have the song files. I cannot get the new app to recognize the old files, so I need to redownload 8 or 9 Gigs of music. On my 2 mb/s rural internet connection, that takes a while.

Does anybody know of a way to preserve Rdio offline songs when flashing a new ROM?