Since shn is lossless and flac is lossless why not convert you shn to flac? Pretty simple script to make. Probably some already built tools to do it also.
Just to point out, lossless on a portable device has issues. Mostly being that the battery life is reduced a great deal. I know for the iPods the 11-12 hour battery life playing mp3s is reduced to about 4 hours when playing lossless codecs. This is due to the fact that the harddrive is accessed 4-5x as much with lossless than with lossy codecs.