Convert POST RPC Service to a RESTful GET Resource

I am trying to expose a legacy RPC service that requires a POST with a JSON body as a Restful GET resource in Kong. I am using the request-transformer-advanced, file-log and correlation-id plugins. When I call the kong/public API, I get back a HTTP 404. I assume that I have the transformer plug-in misconfigured, but I can’t find the backend service POST in the log files, so I can’t troubleshoot the problem.

Two questions:
1 - How can I enable logging from the Kong service to the backend service, so I can see the actual “curl” string that it is using to invoke the backend service?
2 - Has anyone ever done this? If so, any pointers?