Dev notes says there is a Block Forge Cooler. I don't see another Black Forge extension, perhaps some of the previous ones can be built near a Black Forge? If the level 2 Carapace is only +6 over Max Padded, it's really underwhelming.

I'd like to know this too. I see the armor/weapons can be upgraded with a level 3 black forge, but no idea what is needed to upgrade it.

Apparently, this is also by design. The best you can manage is level 2 carapace, which only affords +6 defense over the max upgraded padded set.