Quick question: Coop size for bantams

I'm building a bunch of 10 foot by 10 foot pens to separate the different colors of d'uccles I have. I was hoping to build something like a rabbit hutch for each cage, so they'd be somewhat protected from predators at night.
It's not quite what I'm sketching up, but this is a little like what I was planning: http://www.petco.com/product/113408/Trixie-Natura-Animal-Hutch-with-Enclosure-in-Brown.aspx
Basically, a lower area with three wooden walls and one wire wall for scratching around in the early morning with a door into the 10x10 pen, and a little ramp inside going up into the wooden coop and nest box area.
I can't figure out what size would be okay. I was thinking something like 5x3, so it'd just fit in one corner and not dominate the entire run, but maybe that's too big for that size pen, or too small for birds? They'd only be in it at night and a little of the morning, just until the local raccoons and opossums stop prowling around.
Should the bottom cage have more wire walls and fewer wooden ones? Would that hutch size be far too small to hold six adult bantams in? What do you think is the maximum I should have in a 5x3 area at night? Chicks won't be going into those pens until they are close to adult size, so they don't really need to be factored in.
I don't have to have an exact number set in stone, I just need a rough idea of how much wire to buy.

Edit: Forgot to say, the pens are six feet tall so the coop will be six feet tall too.

 

Was always told the minimum was 1.5. Thought it seemed a bit wrong but at least it wasn't as far off the dead minimum mark as I expected.
I feel like I should note, the coop isn't going to be on the outside of the pen, it has to go inside.

Why is it I can only find someone who's already done it after I post a thread? http://thetanglednest.com/2010/02/our-urban-chicken-coop-plan/ That's pretty much what I have been sketching out.