For some reason, I’m able to build Heavy Survivor Boots without any Kevlar. The other Survivor gear looks right, but for some reason all I need for the heavy boots is the rags, leather, base boots, and metal. I would assume this is incorrect behavior, since the material is listed as “Kevlar, Steel” in the description.
I haven’t TRIED this, since the boots take friggin forever to craft, but I would imagine that this implies an exploit to convert random leather and crud into kevlar. Kinda inefficiently, but still.