Set material main texture during FBX import

Does anyone know how to force Unity to always assign the main texture to be the color texture assigned in Maya? In Maya, when you assign a color texture (e.g. UnityProject/Assets/Textures/Texture1.png) to a material, export the FBX and import into Unity, the color texture will be assigned to the main texture of the imported material. However, if you change the color texture assigned to the material in Maya and re-export (e.g. Texture1.png -> Texture2.png) the material in Unity will still use the original color texture (Texture1.png) as the main texture. I have embedded media turned off in the FBX export settings, however, I get the same results with embedded media turned on. I have both of the textures in a folder named "Textures" in the same folder as the FBX. For the FBX import settings, I have Material Naming = From Model's Material. I don't want to have to use Material Naming = By Base Texture Name because I want one material in Maya to equal one material in Unity.

Below is my current code where I attempt to find the color texture assigned to the material in the FBX. However, if I assign "Texture2" to the model in Maya and import into Unity, it prints out "Texture1". I expected it to print out "Texture2"...perhaps I need to use a function other than OnPostprocessModel, something earlier in the asset processing order of operations?

 using UnityEngine;
 using UnityEditor;
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
 
 public class AssetImportSettings : AssetPostprocessor
 {
     void OnPostprocessModel (GameObject go)
     {
         //Get the renderers in the FBX
         Renderer[] fbxRenderers = (Renderer[])go.GetComponentsInChildren<Renderer> ();
 
         for (int i = 0; fbxRenderers != null && i < fbxRenderers.Length; i++) {
             if (fbxRenderers [i].sharedMaterials == null) {
                 continue;
             }
             
             //Go through each material in the FBX
             for (int j = 0; j < fbxRenderers[i].sharedMaterials.Length; j++) {
 
                 string materialName = fbxRenderers [i].sharedMaterials [j].name;
                 
                 //Look to see if there is a texture assigned to the material. Print the name if there is one.
                 if (fbxRenderers [i].sharedMaterials [j].mainTexture != null) {
                     string textureName = fbxRenderers [i].sharedMaterials [j].mainTexture.name;
                     Debug.Log (materialName + "'s Main Texture = " + textureName);
                 } else { 
                     Debug.Log (materialName + " has no Main Texture.");
                 }
             }
         }
     }
 }