Building Coop tomorrow - Nesting Box Q

[LVB]

Hello! My plan has been to build the coop modifying the "8 chickens" coop built by Third Coast Craftsman (bought his plans) to a "34 chickens" coop by enlarging it to 16' x 8' -- his 12" nesting boxes are along the 16' side. Mine will be 128 sq ft indoors with the hardwire-covered metal roof run of 320 sq ft.
Among my growing chicks in my pop-up-tent brooder are 10 of the largest breeds: 2 Buff Orpingtons, 2 Black Australorps, 4 Cochins and 4 Brahmas. Would you recommend 12x15 boxes for the big girls? Or is 14x14 or 15x15 necessary? The 4.5 lb Polish and 4 lb Easter Eggers could have some 12x12 boxes? Yes, I know, they will go into whichever nest they prefer! So make all nesting boxes the larger size for everyone?
Thank you for your advice!

 

[mowin]

My BO and BAs use 12x12 boxes just fine.

 

[LVB]

My BO and BAs use 12x12 boxes just fine.

Thank you!

 

[aart]

"34 chickens" coop by enlarging it to 16' x 8'

I think that might will get crowded.

My nests are 14 x 14 x 16,
details here:
https://www.backyardchickens.com/gallery/albums/nests.7427682/

 

[LVB]

I think that might will get crowded.

My nests are 14 x 14 x 16,
details here:
https://www.backyardchickens.com/gallery/albums/nests.7427682/

 

[LVB]

Aart, I was hoping to hear from you, but am so new to the board that I don't know how to message you yet. We built a very sturdy floor yesterday and per your advice are extending today, also making larger nesting boxes. Sure do appreciate your help. I understand it's ridiculous getting so many chicks my first time, but this is my after-my-husband-died project to keep me busy now that he no longer needs 24/7 care. My WWII Dad always said, "If you're going to do something, do it right or not at all!" I thank you and my chicks thank you.