Add child elements to custom SOAP header in Spring-WS

Question

I am calling a SOAP webservice with Spring-WS. The webservice in question requires me to pass some information in the SOAP header as shown here:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"&gt;
   <soapenv:Header>
      <CustomHeaderElement>
         <clientID>xyz</clientID>
         <wsdlVersion>1.0</wsdlVersion>
         <serviceType>ExampleService_v1</serviceType>
      </CustomHeaderElement>
   </soapenv:Header>
   <soapenv:Body>
   ...
   </soapenv:Body>
</soapenv:Envelope>

I've figured out how to had the top level CustomHeaderElement, but I don't see anything in the Spring-WS API that allows me to add a child element. Here is what I have so far:

WebServiceTemplate template = ...;

template.marshalSendAndReceive(request, new WebServiceMessageCallback(){
    public void doWithMessage(WebServiceMessage message) throws IOException, TransformerException{
        SoapMessage soapMessage = (SoapMessage)message;
        SoapHeader soapHeader = soapMessage.getSoapHeader();
        QName qName = new QName("CustomHeaderElement");
        SoapHeaderElement headerElement = soapHeader.addHeaderElement(qName);
        //would like to do something like headerElement.addChild(clientIdNode);
    }
});

The problem is headerElement doesn't seem to expose any means of actually adding a child. I know I can add an attribute, but that's not what I need for this service call. Does anyone know how I could add the necessary child elements to my custom header?