I did candling of the duck eggs today, batches 1 & 2. Only one in batch 2 seems suspicious as being a, "quitter." Batch 1 is nearly past the point of candling, and me being able to see various tissues inside, but I can guesstimate using the air sack size to see if they are still doing something.
While doing more and more research, I found this rather detailed write up about Muscovy duck egg incubating,
https://www.backyardchickens.com/articles/incubating-and-hatching-muscovy-eggs.63532/And,
https://backyardpoultry.iamcountryside.com/eggs-meat/incubating-duck-eggs-with-chicken-eggs/ 