Is there no easy way to do this? I've had a fairly large number of shorten files uploaded to me recently and rather than keep them in this format I'd like to decode them to wav and encode to mpc. It's entirely possible that I haven't looked hard enough yet but I can't seem to find much information at all on how to do this or what software to use. I'm missing something obvious I'm sure ... could someone clue me in?

MPC can be directly encoded from shorten as long as you have shorten binary in path. Older mppenc packages included the binary, so chances are you already have it. All you need to do is copy the binary somewhere in path and encode your files as if they were normal wavs.

as far as I remember the mpc encoder can encode directly from a shn file.
you just need to put the shn encoder in the mppenc dir.

Hey I wasn't aware of that thanks! I did find the shn encoder/decoder and it's really easy to use but this is even easier. Thanks again.

??? Are you certain that you want to do that?
Why would you want to turn a lossless file into a lossy one anyway? Say you want to listen to them on an mp3 player someday. You will be forced to transcode, risking even further degradation...