Shader code for placing 5 smaller images in different offsets on a larger base image

Question

I'm trying to texture atlas in realtime, with 5 smaller texture2Ds to be placed on a larger base texture2D...

This shader code only shows the first texture and not the others - and even though it is smaller, seems to scale to size of base texture.

Is what I am trying to do possible with shaders? How do we fix / do this?

Shader "Custom/OverlayShader"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _OverlayTex0 ("Overlay Texture 0", 2D) = "white" {}
        _OverlayTex1 ("Overlay Texture 1", 2D) = "white" {}
        _OverlayTex2 ("Overlay Texture 2", 2D) = "white" {}
        _OverlayTex3 ("Overlay Texture 3", 2D) = "white" {}
        _OverlayTex4 ("Overlay Texture 4", 2D) = "white" {}
        _OverlayPos0 ("Overlay Position 0", Vector) = (0,0,0,0)
        _OverlayPos1 ("Overlay Position 1", Vector) = (0,0,0,0)
        _OverlayPos2 ("Overlay Position 2", Vector) = (0,0,0,0)
        _OverlayPos3 ("Overlay Position 3", Vector) = (0,0,0,0)
        _OverlayPos4 ("Overlay Position 4", Vector) = (0,0,0,0)
        _OverlayAspectRatio0 ("Overlay Aspect Ratio 0", float) = 1.0
        _OverlayAspectRatio1 ("Overlay Aspect Ratio 1", float) = 1.0
        _OverlayAspectRatio2 ("Overlay Aspect Ratio 2", float) = 1.0
        _OverlayAspectRatio3 ("Overlay Aspect Ratio 3", float) = 1.0
        _OverlayAspectRatio4 ("Overlay Aspect Ratio 4", float) = 1.0
        _MainAspectRatio ("Main Texture Aspect Ratio", float) = 1.0
    }
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            sampler2D _OverlayTex0;
            sampler2D _OverlayTex1;
            sampler2D _OverlayTex2;
            sampler2D _OverlayTex3;
            sampler2D _OverlayTex4;
            float4 _OverlayPos0;
            float4 _OverlayPos1;
            float4 _OverlayPos2;
            float4 _OverlayPos3;
            float4 _OverlayPos4;
            float _OverlayAspectRatio0;
            float _OverlayAspectRatio1;
            float _OverlayAspectRatio2;
            float _OverlayAspectRatio3;
            float _OverlayAspectRatio4;
            float _MainAspectRatio;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 mainColor = tex2D(_MainTex, i.uv);
                fixed4 overlayColor0 = tex2D(_OverlayTex0, (i.uv - _OverlayPos0.xy) * (_OverlayAspectRatio0 / _MainAspectRatio));
                fixed4 overlayColor1 = tex2D(_OverlayTex1, (i.uv - _OverlayPos1.xy) * (_OverlayAspectRatio1 / _MainAspectRatio));
                fixed4 overlayColor2 = tex2D(_OverlayTex2, (i.uv - _OverlayPos2.xy) * (_OverlayAspectRatio2 / _MainAspectRatio));
fixed4 overlayColor3 = tex2D(_OverlayTex3, (i.uv - _OverlayPos3.xy) * (_OverlayAspectRatio3 / _MainAspectRatio));
fixed4 overlayColor4 = tex2D(_OverlayTex4, (i.uv - _OverlayPos4.xy) * (_OverlayAspectRatio4 / _MainAspectRatio));
fixed4 overlayColor = overlayColor0.a > 0 ? overlayColor0 : (overlayColor1.a > 0 ? overlayColor1 : (overlayColor2.a > 0 ? overlayColor2 : (overlayColor3.a > 0 ? overlayColor3 : (overlayColor4.a > 0 ? overlayColor4 : mainColor))));
return overlayColor;
}
ENDCG
}
}
}

```