Customer Invoice Upload Tool - Can't get extension fields to populate

Question

In the documentation for the customer invoice upload documentation, it says to get the tag for your extension field in the Customer Invoice XML Output. No issues there. But when I add the extension field to the XML for the Customer Invoice Request Service Interface, the field never populates in the generated invoice request. Note that I cannot create a new XML Upload Service interface as a workaround because this is a 3.5 customer system
The extension fields are in a different namespace from the Request Service Interface, so I've tried the two methods below to populate my Advertiser extension field. I've had no luck with either. Here's some sample XML from the beginning of the file. The files are also attached. Any help is appreciated.
[ I also posted on the SCN where I  attached the test files.|http://scn.sap.com/thread/3237936]
Method 1
<?xml version="1.0"?>
<CustomerInvoiceRequestRequest>
<MessageHeader>
<CreationDateTime/>
</MessageHeader>
<CustomerInvoiceRequest actionCode="04" reconciliationPeriodCounterValue="1">
<BaseBusinessTransactionDocumentID>EXT_100001_TALINV</BaseBusinessTransactionDocumentID>
<BaseBusinessTransactionDocumentTypeCode>29</BaseBusinessTransactionDocumentTypeCode>
<ProposedInvoiceDate>2012-09-16</ProposedInvoiceDate>
<Name>hhhc</Name>
<ReferenceBusinessTransactionDocumentID>100001</ReferenceBusinessTransactionDocumentID>
<Advertiser xmlns="http://sap.com/xi/AP/CustomerExtension/BYD/A03DP">
<EXTAdvertiser00163E027E021ED1BFDF09124EFF4876_002>JUDSON</EXTAdvertiser00163E027E021ED1BFDF09124EFF4876_002>
</Advertiser>
<BusinessProcessVariantType>
<BusinessProcessVariantTypeCode>1</BusinessProcessVariantTypeCode>
<MainIndicator>true</MainIndicator>
</BusinessProcessVariantType>
Method 2
<?xml version="1.0"?>
<CustomerInvoiceRequestRequest>
<MessageHeader>
<CreationDateTime/>
</MessageHeader>
<CustomerInvoiceRequest actionCode="04" reconciliationPeriodCounterValue="1">
<BaseBusinessTransactionDocumentID>EXT_100002_TALINV</BaseBusinessTransactionDocumentID>
<BaseBusinessTransactionDocumentTypeCode>29</BaseBusinessTransactionDocumentTypeCode>
<ProposedInvoiceDate>2012-09-16</ProposedInvoiceDate>
<Name>hhhc</Name>
<ReferenceBusinessTransactionDocumentID>100002</ReferenceBusinessTransactionDocumentID>
<n1:EXTAdvertiser00163E027E021ED1BFDF09124EFF4876_002 xmlns:n1="http://sap.com/xi/AP/CustomerExtension/BYD/A03DP">JUDSON</n1:EXTAdvertiser00163E027E021ED1BFDF09124EFF4876_002>
<BusinessProcessVariantType>
<BusinessProcessVariantTypeCode>1</BusinessProcessVariantTypeCode>
<MainIndicator>true</MainIndicator>
</BusinessProcessVariantType>

Answer 1

Hi Judson,
Thanks for sharing this answer, i am also facing the same issue. But here in my case i have extension field in Items nodes and also got the xml node from customer invoice xml, like below but when i process the xml it adds invoice request but dont maps th "test" nodes data to that extended column.
<n1:test_0LIGMSME2T388H1SZMFGTNHGN_Y38WD8BTY xmlns:n1="http://0008768412-one-off.sap.com/Y38WD8BTY_">test data</n1:test_0LIGMSME2T388H1SZMFGTNHGN_Y38WD8BTY>
Could you please suggest what i am missing.