Well, I completely cracked the composite USB driver deal! I now have a serial USB interface transmitting/receiving while an audio interface works as an audio input to macOS / Logic. Very happy, indeed! There's a little work to be done on the packet code/decode, but not much, really. This opens up the ability to configure/reconfigure DSP modules on the fly which is insanely cool. You might say I on the way to creating a software-defined DSP system.