Binding a library project with a private interface

I'm binding the latest version of the JanRain SDK, I have built the library project in the normal way and added the zip to my binding project, set a bunch of transforms in the metadata.xml and it's generally working without complaint, except for one thing. This interface in the `JREngage' class:

/**
 * @internal
 * @hide
 */
private interface ConfigFinishListener {
    void configDidFinish();
}

I've added the following metadata entry:

<attr path="/api/package[@name='com.janrain.android.engage']/class[@name='JREngage.ConfigFinishListener']" name="visibility">public</attr>

Which does make the bound Interface public, however when I try to use the DLL from the binding I see this error message:

com.janrain.android.engage.JREngage.ConfigFinishListener has private access in com.janrain.android.engage.JREngage
com.janrain.android.engage.JREngage.ConfigFinishListener
\obj\Debug\android\src\mono\com\janrain\android\engage\JREngage_ConfigFinishListenerImplementor.java

Is it possible to override this and make it work, or shall I just edit the source locally and rebuild to set this interface to public?