brent installing to the usb was an option in live .iso. unsure if it still is.
Yep, still is. The USB drive was in the drop-down list of destinations. And the installation worked fine, as far as I could tell, up to the point where it almost finished, but instead displayed a message, "Flushing buffers to disk... please wait" and the progress bar continued to indicate progress, but stays that way for many minutes.
I wanted to label the tag fastened to the live USB, as I'd just burned it, so I removed it and left the destination USB to finish flushing its buffers. But about 10 minutes later (for a total of maybe 15 minutes in all) with no end in sight, I put the live USB back in and re-did the installation. Now that installation is behaving the same as the first one. I think I'll go on to something else on another computer and let it "flush buffers" for a good long time.
EDIT: That seemed to do the trick. Eventually it finished normally, and I was able to remove the live USB and attempt to boot with the newly installed USB drive. It took a while, but as I was typing this it finished booting and I'm ready to log on. Agghhh ... it's too slow to use for my intended purpose. It would take me an hour to demonstrate Solus to someone using this method. A USB 3.1 connection is supposedly about the speed of an eSATA connection, but apparently not this USB 3.1 connection.
Installing 418 upgrades as I type this. Seems to be running at a very normal speed now. I'm going to go ahead and configure this, even if I just keep it as a souvenir. It's been an interesting ride, and now I can say I've done it.