Updated 11/03/2021:
After much effort, fitting, cutting, re-fitting, and working in the cramped Staging Area, the duct work is finished!! I've got a tiny bit of effort left - weatherstripping and possibly some final fit-and-finish work, but the major effort is over!
Sorry, no photos or details because the effort is being teed up for a future magazine article.
I am expecting the smoke generator in the next 4-5 days and then we'll give the entire system a serious test.
More when I know it.
George