Didn't work for me when I tried to apply the .app to a game forwarder. It's possible that it only works for apps and not games, but I do not know much about the scene to give an accurate assessment.
Here's what I did.
1. Downloaded Loadstructor-1.7+cLoader-1.6
2. Created a WAD from a game (Donkey Kong Country Returns) from my HDD (WBFS)
3. Extracted the WAD with ShowMiiWads 1.4
4. Took the 00000001.app provided and overwrote the one that was in the WAD.
4. Created a new WAD with ShowMiiWads 1.4
5. Loaded the WAD in Loadstructor to verify if it is being recognized correctly.
6. Installed the WAD with MMM and tested...
Results: Black Screen