nest box opening size? Is 8 1/2" by 10 1/2" okay?

[wahmommy]

I am going to have external nest boxes, and I wanted the entrance to them to be arched like in this coop:

http://www.theartofdoingstuff.com/the-coop/flickr/6039162346/

I don't know how big the openings in this coop are, but I measured my old coop's pop door and it was 8 1/2" by 12 1/2" and the chickens use it fine. I took this photo and enlarged it and it looks like it would be (if I assume the width is 8 1/2") only 10 1/2" tall. Is that tall enough for a nest box opening?

 

[chickentooth]

The opening is fine as long as when they get inside they have a bit more room 12x12 is considered perfect, but depending on bird size and other factors such as how much bedding is in the bottom. I have 12x12x12 boxes but the opening is only 12x9 and i fill it with bedding so really it ends up about 12x12x9.

 

[wahmommy]

The opening is fine as long as when they get inside they have a bit more room 12x12 is considered perfect, but depending on bird size and other factors such as how much bedding is in the bottom. I have 12x12x12 boxes but the opening is only 12x9 and i fill it with bedding so really it ends up about 12x12x9.

The inside is going to be 11 3/8" wide x 16" deep by 14" tall - does that sound like it would work?

 

[wahmommy]

The lip will be about 4" high to keep bedding in

 

[Quadzilla32]

Adding finishing touches to my nesting box and starting to realize the openings for the box looks to be on the smaller side but I'm not sure if it will work. Currently the box is 12" high in the back and roughly 17" in the front. My concern is that the opening to get into the box is only 9" tall. Will the chickens still be able to get in? I would think they would hunch over and walk in but I don't know. Once they get into the box they have good amount of room each divided section is 12"x12" and has three separate compartments and plenty of pace to stand up.