Oh another idea I had to help people learn how to put the parts together is to post an example asset forge project or unity scene, such as the one in your screenshots.
Yes. Normals are flipped on the cave top corner. I've been meaning to fix it. The kit in general isn't user friendly for the caves in general. You should really create some assemblies in MAST with premade sections. As far as creating samples or tutorials, I'm not going to be dedicating any more time to this kit. The new modular terrain kit will be much easier to assemble whenever it gets finished.