First-person arms with third-person model shadow + first-person animations

I am creating a first-person game, but I want animations on the arms, while still having the third person shadow. I have been doing some research on achieving just that. Turns out in Unity 5 there is a way to cast shadows only source : http://answers.unity3d.com/questions/269292/having-an-invisible-object-that-casts-shadows.html

I have tried doing so, but my (hidden) mesh also has shadows, and I don't know how I would remove them. The edges and bumps on my model still make shadows on the model, which i don't want. I do still have the full model shadow on the ground, so thats what I want. See this example in the game tab, you can actually see the character move http://i.imgur.com/wqQAqLa.webm

Now my question is if there is a simple way to remove those shadows on the model while keeping those on the ground (maybe a shader?).

Now for putting arms for the first-person view, I understand I'll need to use layers (one for first person, and one for the full body in case of networking). Am I able to cut the body and head from my mesh in Blender and only use the remaining parts with the same animation, or will I have to create a new animation for first-person only (with the curt body parts)? I couldn't find anything about this, so a guide or explained example is welcome.

P.S. I can't just move the camera a little in front of the object, because it will clip and that causes the player to see the inside or the back of the head, and if I move it too far to the front I can't see the arms.