PCSAT-2 was supposed to have a PSK31 experiment: 10 meters (SSB XCVR)
up, and 70cm or 2m down, with the audio riding on FM. In theory, at
least, it could be operated full duplex from a really cheap station. I
think they terminated the experiment before I had a chance to check it
out.

Did anyone have any experience with this?

Apparently, the Midshipmen are planning another satellite with the same
mode (plus APRS) for launch in December.