How to set second material to a second submesh in a combined mesh?

I have this code (not originally my invention) that is working fine, but I have hit upon a problem with it. I can't seem to render the second submesh, with another material... it is not rendering at all.

I can't figure out the problem lies in [renderer] part or the 2nd "submesh" that is perhaps never combining.

 @script RequireComponent(MeshFilter)
 @script RequireComponent(MeshRenderer)
 private    var matarray : Material[] = new Material[2];
 var mat : Material;
 var mat2 : Material;
     
 function Start () {
     matarray[0] = mat;
     matarray[1] = mat2;

     for (var child in transform)
         child.position += transform.position;
     transform.position = Vector3.zero;
     transform.rotation = Quaternion.identity;

     var meshFilters = GetComponentsInChildren(MeshFilter);
     var combine : CombineInstance[] = new CombineInstance[meshFilters.Length-1];
     var index = 0;
     for (var i = 0; i < meshFilters.Length; i++) {
         if (meshFilters[i].sharedMesh == null)
             continue;
         combine[index].mesh = meshFilters[i].sharedMesh;
         combine[index++].transform = meshFilters[i].transform.localToWorldMatrix;
         renderer.sharedMaterials = matarray;
         meshFilters[i].active = false;
     }
     GetComponent(MeshFilter).mesh = new Mesh();
     GetComponent(MeshFilter).mesh.CombineMeshes(combine);
     renderer.active = true;

     //here seems to be the trouble.
     renderer.sharedMaterials = matarray;
 }

Alternatively I have tried,

 renderer.sharedMaterials[1] = matarray[1];

In short, I'm in trouble. I have to save few draw calls, which is not looking good unless this gets fixed.