Double sided thin with opaque textures

[Yiqin]

First off I am a beginner
I have models for work that are fairly high geometry to keep it manageable in sketchup (and exportable to 3d pdfs) I use a single surface to represent 0.021-0.031 formed copper. In real life these copper surfaces are bare (left to naturally oxidize) on the outer/convex surface and receive a (artificial) turquoise/blue patina on the inside/concave surface. The attached picture shows two different sizes of the same model with the nice ornate copper texture.

Is there anyway to achieve this with the double sided thin? Or other workable solutions I would rather not need to build more than one set of product models?

Everything I've read on the double sided thin is deals with translucent or transparent. I'm not even sure if in my attempts I'm even setting up the material options.

I am working with some basic photo based textures for both (I plan to improve them and try some uv mapping plugins or project the textures). I was using RT under trial a few weeks ago but I am now using Indigo Render 3.4.19 with Sketchup 2013 Pro skindigo version is whatever was current a week ago but I will get to the latest update asap.
Appreciate the help!

[CTZn]

You can try to set the r_f parameter to 1.0 then play with the front and back settings but this is not the purpose of the Double Sided Thin material.

You would better pull out the shapes for some depth and use SU ways to assign them different materials back and forth.

[Yiqin]

Thanks CTZn, your help added with the 3.6.25.2 skindigo update have helped. I'm pretty sure that I am on a workable track now. I know that having an actual solid would be better but its not very practical for the ways I use my models at work.

Here is my current method:
I gave the desired surface a new material front and back -just a solid white texture
In the skindigo material editor I set the new white material to double sided thin
In the double sided thin settings:
I added the Patina texture to one side (diffuse photo texture)
I added the ornate copper texture to the opposite (indigo material database)
I set the r_f to 1

Now I just need to figure out how to better map the textures. My current method won't allow projection because i'm not directly applying the desired textures anymore. I also have some work to do on my patina texture and a suitable to project copper texture (I really like the ornate copper one though).

Attached is another sample using the above method to double side a single surface