Whenever I insert a body part mesh (let's say ROBLOX 2.0), it comes out in the wrong direction. I have to rotate it to actually get it right. That's not the real problem, though. The real problem is that when I do the same thing but for the torso, it comes out in a really weird shape that can't be fixed by rotating it because it doesn't even look like how it's supposed to.
The real problem is the torso.
This is because those things are not ment for MESHES. They are ment for http://wiki.roblox.com/index.php?title=API:Class/CharacterMesh
CharacterMeshes link themselves to the coresponding bodypart (Right arm, left arm, Left leg etc.)
For R15, i don't know how this works.
All you have to do is switch your Meshes inside the part to CharacterMeshes inside the Character, and link them to the correct bodyPart.
Hope this helps.