First, do you need to release your podcast in stereo? If it's dialog based, probably not. Keep in mind that a 192k stereo file is actually two 96k mono streams (left and right channel) in one file. So if you want the same exact quality, but half the file size, encode a 96k mono MP3 file. Done. At the worst, your music won't be stereo but in a full length show, how many music drops occupy your show really? Not much. It's dialog driven. The voice is the most important part, so it might not matter much and be a worthy tradeoff to sacrifice stereo for the music in your show for the smaller file size associated with a mono file.