I thought there was a horrible mismatch lurking in the definition of substitution extension, but upon closer inspection, it looks okay. I finished the hard case of soundness tonight. I'll try the other four or five tomorrow. They should be easy.
Up to 5292 words, 192 over my 1700/day goal, but tom7 and heather are still beating me. None of the three characters have met each other yet, and have engaged in a grand total of, like, two lines of dialogue, which occurred between character number three and some off-screen extras. Plenty of monologue, though, internal and external. Sooner or later I will have to make them collide. Maybe around the 10,000-word mark, I think. That gives me a few more days to set things up.
After KGB, cajoled
During some other expermentation on the keyboard at home, discovered I really love the sound of a bVI-V transition in the ninth and tenth bars of the blues. Trying to work out some sort of sometimes-bIII-for-IV substitution to go along with it, but nothing good has come to me yet.