iOS shader scale issue

Hey guys, I'm using this shader as material for some characters in a game I'm working on. It works great but there is an issue when I deploy the game to iOS, it seems it loses the objects scale information in the matcap lookup and gets a bit screwed up.. it's working perfectly on the editor. If I multiply the matcap lookup coords (vn * 0.5 + 0.5) for the objects scale the result is correct in iOS. I've searched in the forums but I can't find other people with the same problem. Has any one run into this? Could this be an issue with the iOS rendering code or am I just doing something stupid?

Shader "MatCap" {

Properties { _MainTex ("Diffuse (RGB)", 2D) = "white" {} _BumpMap ("Bumpmap (RGB)", 2D) = "bump" {} _MatCap ("MatCap (RGB)", 2D) = "white" {} }

Subshader { Tags { "RenderType"="Opaque" } Pass {
CGPROGRAM #pragma vertex vert #pragma fragment frag #pragma fragmentoption ARB_precision_hint_fastest #include "UnityCG.cginc"

     uniform float4         _Color;
         uniform sampler2D     _BumpMap;
         uniform sampler2D     _MatCap;
         uniform sampler2D    _MainTex;
         uniform float4         _MainTex_ST;
         
         struct v2f 
         { 
             float4  pos   : POSITION;
             float2  uv       : TEXCOORD0;
             float3  TtoV0 : TEXCOORD1;
             float3  TtoV1 : TEXCOORD2;
         };
        
         v2f vert (appdata_tan v)
         {
             v2f o;
             o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
             o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
             
             TANGENT_SPACE_ROTATION;                    
             o.TtoV0 = mul(rotation, UNITY_MATRIX_IT_MV[0].xyz);
             o.TtoV1 = mul(rotation, UNITY_MATRIX_IT_MV[1].xyz);
             
             return o;
         }
         
         float4 frag (v2f i) : COLOR
         {
     float3 normal = tex2D(_BumpMap, i.uv).xyz * 2.0 - 1.0;
             normal = normalize(normal);
             
             half2 vn;
             vn.x = dot(i.TtoV0, normal);
             vn.y = dot(i.TtoV1, normal);
             
             float4 color = tex2D(_MainTex, i.uv) * tex2D(_MatCap, vn * 0.5 + 0.5) * 1.5;
             color.a = 1;
             
             return color;
         }
     ENDCG
 }

} }