Unity C#- dynamic skyboxes, get no errors but doesn't work

Question

After lots of googling have gotten my C# code to compile without any errors, but it still isn't working. ie my skybox isn't changing.
I've confirmed that my pathing is correct.
I think it must have something to do with how I am referencing the skybox. My understanding is that there are essentially 2 ways to change, update a skybox via code. One is via RenderSettings.skybox and the other is by referencing the skybox on the Main camera. I am using the former approach. The following code is on an empty Game Object. Can any Unity C# gurus help?

using UnityEngine;
 using System;
 using System.Collections;

 public class LoadSkyBox : MonoBehaviour {

      private readonly string[] skyboxTextures  = {"_FrontTex", "_BackTex", "_LeftTex", "_RightTex", "_UpTex", "_DownTex"};

  IEnumerator LoadImg (String skyboxName){
     WWW[] www    =  new WWW[6];
     String tempStr;
      for (int i = 0;i < 6; i++)
      {
           tempStr ="file://"+ Application.streamingAssetsPath + "/" + skyboxName + skyboxTextures[i] + ".png";
           Debug.Log("tempStr ="+tempStr);
         www[i] = new WWW(tempStr);

      }
     //Material mat = GetComponent<Skybox>().material;
      for (int i = 0;i < 6; i++)
      {
          // wait until the download is done
           yield return www;
         //mat.SetTexture(skyboxTextures[i],www[i].texture);
         RenderSettings.skybox.SetTexture(skyboxTextures[i],www[i].texture);
      }
  }

  void Start () {
      StartCoroutine(LoadImg("beach"));
      // Images should be named:
      // "beach_FrontTex.png"
      // "beach_BackTex.png"
      // ...
  }
 }