I have 4 sows in a 2x6 C&C. Two are almost 3 years old, then a 1.5 year old and a 5 month old.
Everyone gets along fairly well and I think they fit just fine. Bigger is always better. Make the cage as large as you can. A 2x6 is the absolute max that would fit in my space so that is what I went with.
I have mine as a an L-shape, it's really a 2x5 with a 1x2 section sticking out the one end.
My girls are really good about sharing things so we have 1 kitchen area, it's a bit bigger that 1.5×2 grids. Disposable bedding and hay go there. I have one big pellet bowl (none are huge pellet eaters so there isn't competition around the bowl). 3 water bottles (2 in the kitchen and one at the other end). 4 hides (a step stool, a fleece forest and 2 log bridge tunnels).
I don't really have any photos of the cage and I'm back at home with my girls for Thanksgiving for the weekend. Next week when I'm back at my student house I can take detailed photos.
At my parents house they share a 15 sqft closet shelf cage. It's a bit smaller but they are get along well. It's the same kind of set up as above, just laid out differently as the cage is 3x5 feet.