I actually have the 2 I started out with and they work perfectly fine, 2 5X4 1/2 stalls that have a solid half wall and door on the bottom and slats spaced 1 1/2 inches apart at the top, it works for me and since it's a limited space I have to work with I try hard to keep my girls spaced at least a week or 2 apart so the new ones get to spend quality time with mom and grow a bit before they join the others, I've used these for 7 years and had no issues with them being too small, very cozy for babies born when mine have been..in the winter!
oh ok i was thinking that i'd have two 5x3 pens. i only ever have two does at a time kid with a month or so in between pairs. i just didn't want to cramp them up in a little pen. i've been desiging a barn for my hay and the kidding pens. i plan to have the kidding pens relatively easy to take apart. i only have spring babies and fall babies i'm trying to get it to where ionly hve spring though.
Those would be big enough, I have mine in a 10x10 area that also has my milk stand and grain can, another area for hay storage is on the backside of the stalls that is 6x6 and is insulation when full...I have mine permanent because I also use them for graining the girls separate, the main barn area for my girls is 8x 12 and suits them well, I have my entrance where the kidding stalls are so it's practical to have the bottom half solid so the newborns don't catch the draft when I enter the barn.
I have two permanent 5 x 6 foot stalls and two 5 x 4. I can take a divider out of the two 5 x 4s making it a 5 x 8. That's good for big litters or bigger does. If I have some first fresheners who look like singles, then the 2 smaller stalls work out. I have an area where I can put up more stalls as well. Size depends on how many I need and how big the does are.
We're hoping to get a new addition built on to the barn soon. It'll be another addition of 10 x 20 to our barn. I will move some of my stalls to that and add another one or two and use the other area as the baby barn. We also plan to put a milk/feed room in the barn too.