Clueless with ember-cli-postcss

I'm trying to do an ember build that uses autoprefixer. The problem that I'm having is that what normally outputs to 'assets/application-name.css' now outputs to 'app/styles/app.css' and I would like to output it to 'assets/application-name.css'.

I have tried adding the outputPaths option, but that doesn't seem to have any effect.

var EmberApp = require('ember-cli/lib/broccoli/ember-app');
var Funnel = require('broccoli-funnel');
var autoprefixer = require('autoprefixer');

module.exports = function(defaults) {
  var app = new EmberApp(defaults, {
    outputPaths: {
      app: {
        css: {
          'app': 'assets/application-name.css'
        }
      }
    },
    postcssOptions: {
      compile: {
        enabled: false
      },
      filter: {
        enabled: true,
        plugins: [
          {
            module: autoprefixer,
            options: {
              browsers: ['last 2 version']
            }
          }
        ]
      }
    }
  });
...