I'm an Architecture student designing and building my own coop this week. I have everything laid out, but am not sure what nesting box size would be best for large breed hens? I have a handful of pullets that won't be laying for a few months. The breeds range in size from Buff Orpingtons (full size not bantam) to a few petite silkies. I'll have a total of 10-12, hens only, but mostly large breed. So what size is best? Thanks!