Word, you're entirely right, of course - the structure should be thought about and made watertight right at the start of the planning, or everything else goes to hell in a handcart. I'm already doing this in advance as I think myself towards novel 2, which involves a contemporary frame about the making of a film and the discovery of an archive, and the discovered archive then comprises an embedded narrative from the 1930s. I imagine that being a crime writer, you have to be particularly exact about structure?
BUT I made a bunch of classic debut novelist errors with his one, mostly caused by writing the individual narratives 'straight through', rather than thinking about how the two parallel narratives would need to counterpoint one another as I went. It's also based very closely on historical people and events, so I'm stuck with certain time parameters. One big issue is that while one narrator's plot reaches back as far as her childhood, the other narrator's plot doesn't start until she's in her late teens, and is far more focused on her own (dramatic) recent past. Which feels a bit ungainly.
Green, I agree Carol Shields is very good - Banville at his best is very good, but I think at times he almost self-parodies. (Plus he's such a dreadful man I can never entirely forget that when reading him, unfairly...) I forget whether I've read The Untouchable, though.
I would know, now, never to do this again, ever, believe me, but I can't actually fully rectify any of these structural issues now, not without actually scrapping it and writing an entirely different novel. I can't ditch one narrator, because the link is both narrators' relationships with a famous man and his mistress. The best I can do is damage limitation now.
Butterfly, do say more about your structural options...?
At least it's cooler! How is everyone else's work going?