Looks like I need to adjust my plans after a big Doh! moment. My current cassette is actually an 11-40, not 42. Not that that matters in the grand scheme because I was planning to use the original 11-32 on my spare rear wheel for Zwift. Of course, I'm not going to be swapping chains each time I want to Zwift, too.

Looks like I need to decide whether I want to stay with the 11-40 or go back to 11-32, and then buy another cassette to match. Doh.