I have the Amish 5X8 and I have 10 chickens. It is perfectly roomy for all of them with roosting space left over. I have a 20X20 fenced run with the coop inside. The coop does take up ground space in the run. Everything works great now. It has 8 nesting boxes and so far only 2 or 3 of them are used. I even have room for a small gardening bench I keep in there so I can sit inside when the weather is not good. I have made a sort of playground for them in the run to give them lots of things to roost on and hide under. I will keep working on their playground so they do not get bored.
OK, now the bad news............I ordered 8 more chicks for April delivery, (you all know how that goes!), and I know I am going to upset the apple cart. They are all bantams and 6 of my original chickens are bantams. A while back, I ordered a 4X4 as integration or isolation coop in case I needed it . It has as small pen attached to it but it will not afford the security of my big coop unless I put it into the totally enclosed pen. I am thinking that I may move it into the pen which will give them more coop space. It will not have electricity like the big coop but my chickens do not seem to mind the cold. In fact the ones that stay out the longest are my silkie couple and I though they needed to be kept warmer. The big coop stays at around 30 degrees with the aid of a flat panel heater.
Just thought I would let you know how things are working out for someone who owns the 5X8 coop you had mentioned. I do love it and it is very well made.