brisket weight loss during cooking, what percentage do I use to figure out how much I need to cook. not the only meat

See also the article here by Kelly Vaughn, “How much brisket do I need to buy?” (2022).
It recommends a lb raw per adult and half a lb raw per child, because the fat on brisket - unlike on some other cuts - needs to be trimmed, and doesn’t melt during cooking.
Sounds high to me, but maybe worth erring on the generous side.

Links about quantities of raw brisket needed per person:
https://food52.com/blog/27276-how-much-brisket-per-person
https://virginiaboyskitchens.com/blogs/features/how-much-brisket-per-person-you-need#:~:text=Choose%20one%20pound%20per%20person,kids%20on%20the%20guest%20list.