Your nest boxes seem to be of adequate width. However, the head room inside a nest box should allow the hen to stand up in it. This is critical because a hen needs to stand up for gravity to assist the egg in coming out of her.
Also, unless the nests are close to floor level, a hen needs a landing perch outside the nest when hopping up. They aren't capable of flying directly into the nest opening like an owl can.
Heavy breeds really should not have roosting perches much more than a foot off the floor. This is because after two or three years of growth, they become heavy enough to do great damage to legs and feet when dismounting a higher perch.
Poop boards needs to be two feet wide so they can catch the poop whether the hen faces forward or backward. Sometimes folks forget hens aren't soldiers in boot camp that will always face the same direction when sleeping.
