trigger of action-observer on a submission get

help! can someone please tell me how to get the second 'action-observer' to trigger immediately after a submission get occurs?

my xforms code needs the attribute 'show' present (for expand and colapse purposes) on every node of a loaded xml data file being loaded from exist. the option to embedded that attribute on every node for every data file is prohibitive so performing the append-attribute action on a data load is the only viable option. i have successfully tested the nested append-attribute script in an orbeon sandbox.

  <xforms:submission
    id="load-submission"
    serialize="false"
    action="http://127.0.0.1:8080/exist/rest/db/gios/eml/{{xxforms:instance('parameters-instance')/eml-ver}}/{{xxforms:instance('parameters-instance')/document-id}}"
    validate="false"
    method="get"
    replace="instance"
    xxforms:instance="document-instance"
    f:url-type="resource">
 
  </xforms:submission>
 
  <xforms:action ev:observer="load-submission" ev:event="xforms-submit-done">
    <xup:modifications version="1.0">
      <xup:append select="//*">
        <xup:attribute name="show">y</xup:attribute>
      </xup:append>
    </xup:modifications>
  </xforms:action>

thanks in advance. - Raul