nested XML using REST

My Simulation model looks like this:
class Simulation < ActiveRecord::Base
   belongs_to :user
   has_many :resources
   has_many :loads
   has_many :distributions
   has_many :buffers...

My Load model:
class Load < ActiveRecord::Base
  has_many :load_dist_links
  has_many :distributions, :through => :load_dist_links
  belongs_to :simulation...

My Resource model:
class Resource < ActiveRecord::Base
   has_many :rsc_q_links
   has_many :rsc_dist_links
   has_many :distributions, :through=> :rsc_dist_links
   has_many :buffers, :through => :rsc_q_links
   belongs_to :simulation...

http://localhost:3000/simulations/4.xml uses this show method:

def show
    #@simulation = Simulation.find(params[:id])
    @simulation = current_user.simulations.find(params[:id])
    @resources = @simulation.resources(force_reload = true)
    @distributions = @simulation.distributions(force_reload = true)
    @buffers = @simulation.buffers(force_reload = true)
    @loads = @simulation.loads(force_reload = true)

    respond_to do |format|
      format.html # show.html.erb
      format.xml { render :xml => @simulation.to_xml(:include=> [
:buffers, :resources, :loads, :distributions])}
end
  rescue ActiveRecord::RecordNotFound => e
    prevent_access(e)
  end

which gives me the following XML:
  <?xml version="1.0" encoding="UTF-8" ?>
- <simulation>
  <created_at type="datetime">2008-09-10T22:15:28Z</created_at>
  <desc>Standard Server Simulation</desc>
  <id type="integer">4</id>
  <name>GroceryStore</name>
  <run_length type="float">8.0</run_length>
  <time_units>hr</time_units>
  <updated_at type="datetime">2008-09-10T22:15:28Z</updated_at>
  <user_id type="integer">3</user_id>
+ <buffers type="array">
+ <buffer.../>
  </buffers>
+ <resources type="array">
+ <resource.../>
  </resources>
+ <loads type="array">
+ <load.../>
  </loads>
- <distributions type="array">
+ <distribution.../>
+ <distribution.../>
  </distributions>
</simulation>

But what I really want is for the distribution that belongs to the
<load> element to be nested inside that element, and the same thing for
the distribution that belongs to the <resource> element.

When I call /simulations/4/resources/2.xml or
/simulations/4/loads/1.xml, I get what I want because I can use :include
on the to_xml statement. But everything I've tried in the
simulations_controller show method, changing the simulation model, even
messing with routing, gives me errors.

For example, I have tried

def show
    #@simulation = Simulation.find(params[:id])
    @simulation = current_user.simulations.find(params[:id])
    @loads = @simulation.loads(force_reload = true)
    @resources = @simulation.resources(force_reload = true)
    @load_distributions = @loads.distributions(force_reload = true)
    @rsc_distributions = @resources.distributions(force_reload = true)
    @buffers = @simulation.buffers(force_reload = true)

    respond_to do |format|
      format.html # show.html.erb
      format.xml { render :xml => @simulation.to_xml(:include=> [
:buffers, :resources, :loads, :load_distributions, rsc_distributions])}
end
  rescue ActiveRecord::RecordNotFound => e
    prevent_access(e)
  end

but the error is "undefined method "distributions" for the line
@load_distributions=@loads.distributions(force_reload = true).

How can I modify the simulations_controller#show method so that I get
the distributions associated with loads and/or resources to be properly
nested?

LG