Skinned Mesh Renderer - Adding/Removing Materials via C#

I am trying to add a material to my skinned mesh renderer via code. Then later I need to be able to remove it via code and reduce the array size back to 1 from 2. It has to be added, not changed.

What I believe should work isn't working.

public Material leatherArmorMaterial;

^ mtl

GetComponent().materials[1] = mtl;

This doesn't work. It doesn't error and it doesn't do anything.

If I do

bodyGeo.gameObject.GetComponent().material = mtl;

It will change the first material to the prefab loaded into leatherArmorMaterial.

I can't find any other option for adding/removing materials. Can anyone assist me?

Thanks.