I made the six box design and it was working great - but I think I messed up on the plywood. I must have used interior rather than exterior because it delaminated and grew fungus.
So I will be working soon to repair it and use the right materials next time. Now that I have a portable drill and circular saw that are rechargeable and light weight I don't mind the construction as much.
My girls have mostly used the upper boxes and sometimes a few girls will trying laying in one box at the same time. Occasionally I will find an egg in the lower ones but that is rare.
I have found only one drawback - when the girls go broody they will still hang out in the nest boxes and if they are hatching eggs it becomes a challenge to keep their eggs from breaking or rolling away. Last time two girls went broody I ended up giving them day old chicks - which was also a challenge because the chicks would slip under the back and get away from their warm momma. But I blocked the back for a few days while they actually hung out in the nest boxes until they moved their broods to the floor. Otherwise I love the roll out feature.