Well, folks, the script has evolved to a bit more than an experiment. It worked well enough that it is presently the only means I use to operate the Proficio. Because of that, a few refinements were needed:
1- The original version was just a start-up script, with an awkward exit and re-start sequence to change operating modes. Now, version 2 recycles to its beginning and can restart in another mode relatively quickly. I use a desktop launcher to start the xterm that runs the script. That gets parked in a corner of the screen where operating status messages can be seen.
2- Frequency calibration is now automated, including offering pre-set broadcast reference options. The result is saved in a start-up file, along with a bunch of other things.
3- Voice/CW mode has a new GUI with some push-button functions missing in HDSDR. There is a flexible Split Rx/TX capability that can also serve the purpose of RIT. There are six memory presets available per band (except in 60 meters where there are only 5 fixed channels). Adding more presets would be a trivial matter, but six is about all I can keep track of. Band-switching sets HDSDR's mode to a reasonable default for the band. It also remembers the last selections for each band, including Split state, even after power-down and re-start. Set frequencies are displayed as button labels, including for Split RX and TX.
4- The goofy sound system in Linux caused fits initially, trying to get the applications to stay in-sync in terms of I/Q and audio configuration from one power-up to the next. The script now includes invocation of pavu before anything else starts. That, combined with a consistent habit of fully booting the PC before powering-up the Proficio, has resulted in smooth start-up in all modes without having to fiddle with settings. Sequence: Allow the PC to totally enumerate its peripherals, then power-up Proficio and, finally, apply PAVU settings before before invoking sdr applications.
I tried to excessively comment the code, not only to help others figure out how to make it all work, but also to remind me six months from now. However, that, a README, and some other notes are all you get in terms of installation help at the moment. I can't honestly recommend trying it unless you are comfortable fooling around with linux or are committed to learning. That said, I hope others find this useful in some way.
The revised start-up Dialog:
Push-button controls to supplement HDSDR's in Voice/CW mode (Split frequencies are not set in this example. When set, the buttons display frequencies.):