Spacing
From Mother Earth News:
Each doe or buck should have a hutch that's at least 3 feet long, 2-1/2 feet deep, and 1-1/2 or 2 feet high. You can construct the sides and top of a "rabbit palace" out of small-gauge chicken wire, but be sure to use only sturdy (and easy-on-the-furry-feet) 1/2' X 1" galvanized hardware wire for the cage floor. The entire box can be framed on the outside with wood or metal (be careful ... rabbits will chew on any exposed wooden members) and should be constructed so that it stands well off the ground.
9-11 lbs 540 sq in
864 for nursing does
OR
4 sq feet
6 sq feet
Nesting boxes
From Mother Earth News:
Lastly, you should make a nesting box for each doe to use when she "kindles" (gives birth). This bunny nursery can be built out of wood and sized to be about 18-22 inches long by one foot wide by one foot high. Also, fasten a 3- to 9-inch wood strip along the bottom of its otherwise unobstructed front end- to keep the newborns from rolling out- and leave the top partly open to allow ventilation.
This is awesome. Setup for one buck and two does. We can also omit one of the "fattener" pens and switch the does out, if we only have one litter at a time.
How to make a wire cage with J-clips.
Those cages hung on a PVC frame. This would be OK if we didn't have to worry about predators; we'll need a more sturdy setup.
PDF:
This is way too involved, but it might be useful for something.
Another:
This might be useful, too, though it's not exactly right.