I did not go off the plans for the length or height of the roots. My roost bar is a bit shorter (I think around 7'), and is about 6" above the poop tray. Poop tray is about 15" above the floor. I think... we just eyeballed it and put a chicken in there to "try it on" as we went, to make sure it fit. On ours there is plenty of room under the poop tray for them to walk/hang out, which was important to us. I didn't want to lose the floor space. Even the large hens can comfortable walk under there. Some of the pullets have even declared it nest space, and I find eggs under there every day.
I scoop it every other day or so, but it only takes me 5 mins. Scoop it into a bucket, dump the bucket into the compost. I avoid doing it on windy days because of the dust, but with 14 it gets dirty fast. The PDZ really helps keep the smell down.