Using the same URL for multiple nested ember routes

I have a case using Ember where I want to make the top level URL available (ie. localhost:4200/demo), and have all the routes underneath also display the same URL (localhost:4200/demo). So the route file, if possible would look something like:

this.route('demo', function() {
  this.route('one', { path: '/' });
  this.route('submit', { path: '/' });
});

I understand that ENV.locationtype can be set for the whole app, but is there a way to conditionally set this for specific URLs underneath a parent URL?