Outbound ABAP Proxy. Field with initial value removed from the xml

I have a structure in which the fields can be sent the initial value. In this case, FIELD1 declared as an integer type whose initial-value - is 0. I now, optimizer side SAP system operates in such a way that by default does not form the elements xml-message for initial values. Accordingly, the element for the field №1 was not generated. I have to transfer all fields in the SAP PI XI, even if the values in the field is initial or = 0.

According to http://help.sap.com/saphelp_nw74/helpdata/en/48/591b845e024bb9e10000000a42189b/content.htm

i need call method "set_extended_xml_handling", but i don now, where I shall describe a method call?

in the generated class i have:

IF_PROXY_BASIS_INTERNAL~CREATE_FRAMEWORK

IF_PROXY_BASIS~GET_PROTOCOL

IF_PROXY_BASIS~GET_TRANSPORT_BINDING

IF_PROXY_CLIENT~EXECUTE

CONSTRUCTOR

SI_INV_PROJ_AO

method CONSTRUCTOR not modifiable, method SI_INV_PROJ_AO not modifiable to.

Reason:

The entered class is a generic proxy type. These proxy types cannot be

processed using the Class Builder, but using the transaction SPROXY.

Create a new method there is no possibility to.

Where i need to call method SET_EXTENDED_XML_HANDLING of interface  IF_WSPROTOCOL_PAYLOAD before calling proxy?

Could you explain to me step by step?

Best Regards, Pavel.