That's really interesting. I googled Guido and QCX and found the thread on the QRP Labs group and another interesting hit.
I'll include the links here for anyone interested.
/g/QRPLabs/message/30792This is a fun topic with some interesting experimentation going on.?I think FT8 could be generated just by updating the Si5351 over i2c?¨¤ la what CEC did for WSPR in his firmware. But that is a side issue not directly related to the SSB topic.
Yes, the DSP code for a digital approach would be interesting.
Tom, wb6b