Nine in 23 square feet?! That's a bit tight, though I guess it's just above the 2 foot minimum I've seen in some places. What size birds?
Re: the planning, I just went out in the yard with a tape measure.
Columbia city ordinance requires me to be at least 10' from the property line, and at least 25' away from a neighbor's house. The corner I want to work in -- a square space adjacent to the patio and the back of the house -- measures 10'x14'. A good sign!
With a maximum of 6 hens, I'm looking at an ideal of about 60 square feet of open space and 24 square feet of floor space in the coop. If I do a 7'x9' run, I can tuck a 4'x6' coop in the corner and still leave about a yard of access between the run/coop and the house. The house will shelter the whole thing from the North, and if I do a slanted covered run, I can do the tall side on the North and use silvered Suntuf to cover the run and protect my feathered friends from the hot Missouri summer sun (the other concern). Worst case, I could just do a 6'x7' run initially and tack the other few feet on later. Guess it's time to haul out the graph paper and figure out the rest of the set-up!
Also, great call about never adding single birds if I can avoid it. Guess it's 2-3 to start, then pairs every couple of years or so.