You could go ahead & leave the board up, the hen probably won't want to leave the nest for 24 hours while all the babes hatch. She won't want to get up to eat/drink/poop.
*BUT* since you've had problems with other hens pecking at the chicks, you might want to scoop everyone up now and move them to the secure cage. I don't think the hen will abandon the nest while her chicks are hatching. Maybe there's a way you could take the hen off the nest, slide something underneath, like a piece of cardboard, and scoop up the nest, eggs, & chicks all in one piece to carry to the cage. Then reinstall Mama hen with them.
It's your call, and I wish everyone the greatest of success!
