So I just completed a remodeling job inside my 12' x 12' coop. I had a good 4 box nesting box but it was at ground level and bending over picking up the eggs was clearly a poor idea. I had just built it so heavy that I couldn't raise it w/o help. But I built a strong stand and got my brother to help me lift it up. Now those boxes are about shoulder high.
Then I saw the opportunity to build more nesting boxes below the original four. I went with an 'open concept' ... it has a 4" rail and a nice layer of pine shavings and the ladies have taken to it ...but it looks like they have decided it's a two nest box as only one pullet takes one back corner and another pullet will lay in the other back corner.
It looks to me like if I want more pullets to use this nesting box I need to install some dividers .... I suppose I see know why nesting boxes are built the traditional way.