Multiple tex2D commands in fragment shader needed, is there a workaround?

Hi. I have to use multiple tex2D commands in my fragment shader, to make use of multiple uv-sets. Unfortunately this heavily decreases the framerate on my iPod 4G (30fps down to 23fps with just 1 additional tex2D call).

This is a simplified version of my fragment shader (still causing the speed issues):

        v2f vert (appdata v)
         {
             v2f o;
             o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
             
             o.uv1 = v.texcoord;
             o.uv2 = v.texcoord1;
             
             return o;
         

         }
 
         half4 frag (v2f i) : COLOR
         {
            half4 tex = tex2D (_MainTex, i.uv1);
             half4 texcol2 = tex2D (_MainTex, i.uv2);
                                                                                               
             return tex + texcol2;
         }

is there anything i can do to achieve a better performance for this shader (without using fixed function)? Thanks!