Simplest solution that I can give to you:
A. Install your Unity Pro with Android Pro plugins, setup
Cardboard SDK For Unity, install Android Build tools and SDK.
B Setup Skybox
Get a stereoscopic panorama image (Might take a while to load the image as it is a high resolution image).
In Unity, import the image, change the Texture Type to Cubemap. Select the Mapping as Cylindrical (Lat and Long).
Create a Material, change the Shader to Skybox/Cubemap.
Assign the texture to the material.
In Unity 5 Pro topbar, select Window -> Ligthing, drag the material to the Skybox property. In this step you can do it programmatically. Combine these steps with the Cardboard assets and game objects. Voila, you've made a VR panorama stereoscopic Cardboard app! The whole setup is just take out your five minutes(excluding setup your tools :D).
If you're familiar with Unity, you know exactly what to do on my instructions. If you stuck at somewhere in my steps, feel free to ask me. Happy coding :)
Extra tips:
You can make the large textures files into Asset Bundles, act like a dynamic content which is stored in the server. Your app is just simply a small-size empty app. When app launches, request and download the asset bundles from server then manipulate the textures. :)
Super extra tip: Don't forget to generate asset bundles under Android Build Settings. If not, your textures will be corrupted when the bundle is downloaded to Android phones.
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