Make one skinned mesh with weighted bone values take on the bone movement of a main skeleton?

My problem is i am getting a model that has been bone weighted in, this is a piece of armor. When i step through the piece of armour it has only 23 binding poses while the main body i am attaching it to has 29 .. this seems to pinch a bunch of the verticies into a center after i assign the 29 bones from the body mesh to it . 80% of the armour looks fine but the chunks that are moving with the body are all pinched into the center.

Any Ideas?

     public void SetMaterialForSkinnedMesh(SkinnedMeshRenderer renderer, MeshFilter filter, k.RarityType rarity)
     {
        // renderer.rootBone = body.rootBone;
         renderer.sharedMesh = filter.sharedMesh;
 
         Transform[] bones = new Transform[renderer.sharedMesh.bindposes.Length];
 
         for (int i = 0; i < renderer.sharedMesh.bindposes.Length; i++)
             bones[i] = boneMap[i];
 
          renderer.bones = bones;
 
 //         for (int i = 0; i < renderer.sharedMesh.bindposes.Length; i++)
 //         {
 //             renderer.sharedMesh.bindposes[i] = renderer.bones[i].worldToLocalMatrix * transform.localToWorldMatrix;
 //         }
 
         renderer.sharedMaterial = Game.Instance.Materials[rarity.ToString()];
     }