[three_legs]

Sounds very fun and full of interesting challenges. It's not directly applicable because they didn't use underground dwellings, but you might appreciate the book "One Straw Revolution" for the spirit of community and simplicity of growing food. Maybe some people on permies.com would be interested or have advice.

[jelliclesfarm]

Yes. I am a member there. Very interesting stuff. Won’t necessarily scale, but I am not looking to scale. 200-250 seems you be the dunbaresque number for a subterranean community.