using builder rxml template in model

Hello,
  Im trying to decide the best way to implement an interface to
quickbooks using xml.
I have

class Timecard < ActiveRecord::Base
  has_one :quickbook
  after_create :quickbooks_add_timecard #this method calls
self.quickbook.add_timecard
end

the thing is that I thought it was gonna work out great, I could put
all my xml templates in a views directory and have everything nice and
organized. The problem is that It seems like this operation should be
triggered from model callbacks, and I would lilke to put somethign like
this in the quickbook.rb model:

class Quickbook < ActiveRecord::Base
  belongs_to :timecard
  def add_timecard
    request_xml = render_to_string :template =>
"quickbooks/add_timecard"
    send_data(request_xml)
  end
end

I see 3 options:
  1.) move this callback logic out of the model and put it in the
controller in the first place.
  2.) use Builder::XmlMarkup directly in the model, to generate an xml
request strig, loading the templates directly,
        load "app/views/quickbooks/add_timecard"
  3.) Figure out how to get a rendered template from within the model
(like shown above)

Option 3 seems the cleanest to me, it just goes against my normal
conventions of putting data model rules in the model. I'd like to
figure out how to do #3 in any case.

Any ideas?

Thanks,
Michael Fairhchild
         The only problem with this is Im not sure