Trying to turn off fog in this Toon/Lit shader

I've got to be doing something wrong. I've got the standard Toon/Lit shader on an object. I right click it in the inspector and go to "Edit shader..." which opens it up in MonoDevelop. I add "Fog { Mode Off }" to the SubShader and save it as a separate "Toon/Lit-noFog.shader" file. Here's the full shader code:

 Shader "Toon/Lit-noFog" {
     Properties {
         _Color ("Main Color", Color) = (0.5,0.5,0.5,1)
         _MainTex ("Base (RGB)", 2D) = "white" {}
         _Ramp ("Toon Ramp (RGB)", 2D) = "gray" {} 
     }
 
     SubShader {
         Fog { Mode Off }
         Tags { "RenderType"="Opaque" }
         LOD 200
         
 CGPROGRAM
 #pragma surface surf ToonRamp 
 
 sampler2D _Ramp;
 
 // custom lighting function that uses a texture ramp based
 // on angle between light direction and normal
 #pragma lighting ToonRamp exclude_path:prepass
 inline half4 LightingToonRamp (SurfaceOutput s, half3 lightDir, half atten)
 {
     #ifndef USING_DIRECTIONAL_LIGHT
     lightDir = normalize(lightDir);
     #endif
     
     half d = dot (s.Normal, lightDir)*0.5 + 0.5;
     half3 ramp = tex2D (_Ramp, float2(d,d)).rgb;
     
     half4 c;
     c.rgb = s.Albedo * _LightColor0.rgb * ramp * (atten * 2);
     c.a = 0;
     return c;
 }
 
 
 sampler2D _MainTex;
 float4 _Color;
 
 struct Input {
     float2 uv_MainTex : TEXCOORD0;
 };
 
 void surf (Input IN, inout SurfaceOutput o) {
     half4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
     o.Albedo = c.rgb;
     o.Alpha = c.a;
 }
 ENDCG
 
     } 
 
     Fallback "Diffuse"
 }
 

Can anyone tell me what I'm doing wrong here? From all the threads I've read this seems like it should work, but no dice.

Thanks!