On the idea about having "two floors" in the coop to increase size of the coop. I did this, somewhat in my coop on the second floor of my barn. It turned out that my "second floor" turned into being the dropping board for my roost. When they are awake, out and about, they are all on the first floor. My coop is 4x5 with a 2x4' plywood board under the roost. There is also a 8" wide x 3' long "catwalk" over to the waterer on the 2nd level.
The gals do hang out on the second floor some during the day. I think it helps with giving them a place to get away from each other.
(HMM, does this mean I can legitimately call my coop 4x5=20 sq ft PLUS 2x4=8 sq ft ... does that mean I can get MORE chickens?! Seriously, I couldn't imagine 3 additional birds in there. Maybe one more, or two bantams.)