Choosing which files to move to Android apk expansion file

I have a problem which came when I decided to split my apk to apk+obb file.

I am using a native plugin that makes file access using Android native AssetManager API. The files that this plugin accessed were placed in a folder in StreamingAssets. This part was working perfectly fine.

Now when I split the apk to obb file, the StreamingAssets folder gets moved to the obb file. There is a different mechanism to access obb file from native code so my app was obviously failing.

Now there are two ways to solve this. I can either alter my code to use native StorageManager API which can then access the files inside obb.

The other solution that I prefer is to prevent this folder in StreamingAssets to be moved to obb file. This is preferable because the files in this folder hold critical game data in xml files which a hacker can easily modify to cheat. I believe obb files can be easily hacked than apk files.

I am not sure how Unity 4's eclipse export works (if it works) and how can I modify the apk+obb packaging step. Please help if you have any idea.