writable mount encrypted obb with StorageManager in Android

Question

1. I need to mount an obb encrypted file writable. Mounting an encrypted obb works just fine but is always readable, so i can't delete files or modify them

   getApplication().getSM().mountObb(mExpansionFile.getAbsolutePath(),
                                      getPass(), mOnObbStateChangeListener);
   

2. Perhaps there is a specific way to create obb files to be mounted writable. Mine obbs are created with the jobb tool.