Thanks all for the comments. Let me take them as I see them.
Cajunhillbilly: Thanks, I'll defintely look for closing vents when I purchase the vents for the bottom.
Elmo: On the ventilation page, yes, I've read it many times. It is thorough, but still confusing.
We don't get hot in Seattle, we get rain... Seriously, we get a week a year above 85 degrees. The window I'm considering in the clean-out door would face west, so it'd get only direct sun in the evening. In the heat of the summer I'd planned on using shade cloth over the window. I just can't think of another place for a window.
As for the "chicken wire" reference in the drawings, that changed immediately. It was never supposed to be chicken wire, but rather welded wire with sufficient thickness to keep out predators. I keep forgetting the reference to chicken wire is even in the drawing.
As for the popdoor in the floor, we have discussed it. We want it to go into the mini-run so it has to be in the floor. Yes, our compromise is to build up the floor there so less bedding falls down. It's not perfect, but as there is no run, we need the hole there.
You are right Elmo, the mini-run is not where the chickens are going to be confined for more than possibly an hour a day, maybe not that long. I can't put a fixed run in my yard, so I will ark them daily in a 4x8 A-frame ark that we will move around the yard every day. We are still figuring the best way to get them into the ark from the mini-run. I should have mentioned the ark originally.
As far as cleaning the mini-run, I planned on raking it out whenever needed. I'm less concerned about predators as our primary culprit around here is the raccoon, which is nocturnal. The birds will be in the predator proof coop at night. I also use predator deterent in my yard to keep them out of my garden. Hmm, I wonder if the birds will react to that. I may have to stop using the dried urine...
Anyway, yes this is a tractor design. It is capable of moving, but I do not intend on moving it often. I like the spot and don't have many other places to put it. My solution is to move the chickens daily in the ark. I will conside an apron also. Thanks! Elmo, you are so helpful!
DDawn: Very interesting thought about only using the six inch by 6 foot vent for ventilation. I plan on 4 birds, so that's not quite 1 SF per bird, but you make an interesting point. I will have to consider that.
Aimiel: I forgot to mention above that this is a mobile coop. For that reason we are planning on Trex 2x4s for the bottom, so they won't rot. The drainage is fairly good there as it is higher than the storm drain 5 feet away. I'm hoping that is sufficient. I've checked the site during this wet winter and it seems good. Great thought though. As for predators taking eggs, there will be two nesting boxes about 3 feet off the ground. I hope I don't need to lock them, but maybe a clip latch isn't a bad idea. Thanks!
Gerry: The coop is raised 2 feet above the ground with the area below wired in for a mini-run. Is that sufficient? The coop will be as secure as we can build it.
Thanks all, I think I hit the high points. Any further comments will be greatly appreciated.