I sometimes run into an issue where when I merge two meshes by copying a node from one mesh and pasting it into another, the piece I copied over doesn't appear in-game. I especially see it a lot when merging something into a mesh with Bip nodes like armor or a creature. One example is adding armor to a creature, or objects to a saddle that goes on a horse. I'm pretty sure it's not a texture issue, since the copied piece has correct textures and normal maps. Sometimes when this happens I've been able to fix it by moving the copied piece under an existing node, but other times it doesn't show up regardless of where I put it. Is this a common issue, or is it just something I'm doing wrong?

Also, in a related topic (maybe even what's causing the above), are there any tutorials that detail how to map parts of a mesh to certain bones?

EDIT: Another related question is this: Is there a way to merge two NiTriShape nodes into a single one? Currently I have to insert a NiNode and then insert each NiTriShape as a child of the NiNode.