Rails: multiple route parameters w/a single model - can it be done?

routes.rb

ZomgMyThings::Application.routes.draw do

  devise_for :users

  scope ":username" do
    resources :things #=> /some-user-name/things/42
  end

  get "/:username" => "users#show", :as => :user_profile

  root :to => 'pages#home'

end

thing.rb

class Thing < ActiveRecord::Base
  belongs_to :user

end

things_controller.rb

class ThingsController < ApplicationController
  before_filter :authenticate_user!

  def create
    @thing = current_user.things.build(params[:thing])
    if @thing.save
      redirect_to(thing_path(@thing.user, @thing)) # YUCK!

      # I'd much rather be able to do this, as @thing has the user already
      redirect_to(thing_path(@thing))
    end
  end

end

user.rb

class User < ActiveRecord::Base

  has_many :things

  def to_param
    username
  end

end

Is it possible to get rails route helpers to fulfill multiple route parameters with a single model? I'm talking about a use case something like nested resources, with corresponding helpers, except the outer resource isn't really named nor explicit.

Does that even make sense?

I'm shooting for urls like /:username/thing/:id - similar to how GitHub does their URLs.