Yes, I was!
You just have to put your manifest.json file into your public folder, but give it a specific name, like your_manifest.json, since manifest.json is already taken by meteor.
Now you can actually reference in your main.html file this your_manifest.json. It is basically possible to use any .json file as the manifest, however only the last manifest reference will be actually used. I think this overrides (meaning, the meta tag in your main.html file will use the custom manifest instead of the one automatically generated) the standard meteor manifest, I am not sure what implications that may have for you (I couldn’t find any problems so far).