XML for Extension Collection of Purchase Orgs on Materials Import

I am having a problem properly formatting some XML.  We added an Extension Collection to the Material Master in Sourcing for holding a list of Purchase Org Objects.  I have been trying to modify the standard XML PI uses when it receives a MAT_MAS IDoc.  I have done many iterations of the XML.  Some that succeed with Warnings and some that succeed, but don't add the Object to the Extension Collection.  I have tried the following.  How do I format the XML so I can add the Purchase Org Object to the Extension Collection?

Import Successful But empty row in Collection          

<collections>

                                <WMT_PORGS>    

                                        <object classname="masterdata.POrg">

                                                <fields>

                                                        <WMT_PORG>

                                                                <EXTERNAL_ID>CA01</EXTERNAL_ID>

                                                                <BUSINESS_SYSTEM>DR4CLNT420</BUSINESS_SYSTEM>

                                                                <DISPLAY_NAME>Purchasing Org CA</DISPLAY_NAME>

                                                                <DOCUMENT_DESCRIPTION>Purchasing Org CA</DOCUMENT_DESCRIPTION>

                                                        </WMT_PORG>

                                                </fields>

                                        </object>

                                </WMT_PORGS>   

                        </collections>

Successful Import But empty row in Collection          

                        <collections>

                                <WMT_PORGS>

                                        <object classname="masterdata.POrg">

                                                <EXTERNAL_ID>CA01</EXTERNAL_ID>

                                                <BUSINESS_SYSTEM>DR4CLNT420</BUSINESS_SYSTEM>

                                                <DISPLAY_NAME>Purchasing Org CA</DISPLAY_NAME>

                                                <DOCUMENT_DESCRIPTION>Purchasing Org CA</DOCUMENT_DESCRIPTION>

                                        </object>

                                </WMT_PORGS>

                        </collections>

Successful Import But empty row in Collection  

                        <collections>

                                <WMT_PORGS>

                                        <object>

                                                <fields>

                                                        <WMT_PORG>

                                                                <object classname="masterdata.POrg">

                                                                        <EXTERNAL_ID>CA01</EXTERNAL_ID>

                                                                        <BUSINESS_SYSTEM>DR4CLNT420</BUSINESS_SYSTEM>

                                                                        <DISPLAY_NAME>Purchasing Org CA</DISPLAY_NAME>

                                                                        <DOCUMENT_DESCRIPTION>Purchasing Org CA</DOCUMENT_DESCRIPTION>

                                                                </object>

                                                        </WMT_PORG>    

                                                </fields>

                                        </object>      

                                </WMT_PORGS>

                        </collections>

Succeeded with Warnings But empty row in Collection    

Succeeded with Warnings

                        <collections>

                                <WMT_PORGS>

                                        <object classname="masterdata.POrg">

                                                <fields>

                                                        <WMT_PORG>CA01</WMT_PORG>      

                                                </fields>

                                        </object>      

                                </WMT_PORGS>

                        </collections>

This is what I mean by "empty row in Collection"