Outside my experience on breed side. There are attributes of the nest and how it is located that reduce egg breakage associated with egg deposition and and incubation process. Key is a flatter nest bowl and the hen having the ability to step rather than jump into nest. Keeping other hens away also helps keep conflicts from putting eggs at risk.Interesting. What do you think of LF Cochins in the broody hen department? Are they so large they are likely to break the eggs?