Compositing a cursor over a rendertexture - GL pipeline problems?

Basically I'm trying to recreate the interactive surfaces in Doom3 using RenderTextures. So far I raycast every frame to see what the player is pointing at, and if it's using a RenderTexture, I get the camera, target texture, and texture coordinates of where on the texture the player is pointing.

The camera-find algorithm is brute force, but there will only ever be a few active cameras in a given Scene, so while alternatives are welcome this won't be too bad of a performance hit.

What I want to do next is display a HTML-esque hand cursor at the specified texture coordinates as a precursor to making and using a simple UI, but it's not working. What am I doing wrong?

Note: This attempt incorporates solutions from other unityAnswers, available [here],[1] [here],[2] [here],[3] and here.

 using UnityEngine;
 using System.Collections;
        
 public class mouseScript : MonoBehaviour {
     public Camera lastrendTexCam;
     public GameObject lastSightedObj;
     public GameObject testObj;
     public Texture2D cursorTexture; 
     string lastScreen = null;
     Ray tempray = new Ray();
     RaycastHit temphit;
     RenderTexture rendTex;
     private int i;
     float wperc;
     float hperc;
     
     // Use this for initialization
     void Start () {
         lastrendTexCam = new Camera();
         lastSightedObj = new GameObject();
         testObj = new GameObject();
         temphit = new RaycastHit();
         rendTex = new RenderTexture(1,1,0);
         i = 0;
         wperc = 0.0f;
         hperc = 0.0f;
         cursorTexture = new Texture2D(128,128);
         cursorTexture = (Texture2D)Resources.Load("UI/hand");
     }
     
     // Update is called once per frame
     void Update () {
         
         tempray = Camera.main.ScreenPointToRay(Input.mousePosition);
         if (Physics.Raycast(tempray, out temphit)){
             print ("Raycasted " + temphit.transform.name);
         }
         if(i == 0 || temphit.transform.CompareTag("Interactive")){
                 testObj = temphit.transform.gameObject;
                 i++;
                 isCamera();
         }
     }
     
     bool isCamera(){
         rendTex = (RenderTexture) testObj.renderer.material.mainTexture;
         Camera[] cameras = FindObjectsOfType(typeof(Camera)) as Camera[];
         foreach(Camera c in cameras){
             if (c.targetTexture == rendTex){
                 lastrendTexCam = c;
                 lastSightedObj = temphit.transform.gameObject;
                 lastScreen = lastSightedObj.name;
                 var pixelUV = temphit.textureCoord;
                 wperc = (pixelUV.x * rendTex.width);
                 hperc = (pixelUV.y * rendTex.height);
                 print (cursorTexture);
                 drawCursor ();
                 return true;
             }    
         }
         print ("Didn't find the RenderTexture target.");
         return false;
     }
     
     void drawCursor(){
         RenderTexture.active = lastrendTexCam.targetTexture;
         print (RenderTexture.active);
         GL.PushMatrix();
         GL.LoadPixelMatrix (0, 2048, 2048, 0);
           Graphics.DrawTexture (new Rect (wperc, hperc, cursorTexture.width, cursorTexture.height), cursorTexture);
           GL.PopMatrix ();                    
           RenderTexture.active = null;
     }
     
     
         
 }

[1]: http://answers.unity3d.com/questions/13512/how-do-you-programmatically-retrieve-the-rendering.html

[2]: http://answers.unity3d.com/questions/16139/when-does-rendertextureactive-myrt-work.html

[3]: http://answers.unity3d.com/questions/23523/pass-clicks-through-camera.html