There was the same problem. Found only to read the XML request
1) Add "client_filters" to the "uses" clause,
2) call RegisterLogFilter();
3) Then, only then, register the logger as in
"TRANSPORT_STRING=HTTP:address=http://127.0.0.1/services/IMyService;FilterString=LogFilter,OutputDir>c:\the\path\you\want"
4) Use the web service,
5) request.log and response.log will saved to the specified folder.
How to configure the request itself did not understand. I generate manually without wst