SOAP -> PI -> RFC without mapping

Hi all,

I searched forum and found a few articles that state that SOAP --> PI --> RFC should be possible. However, I'm kinda stuck here.

Here's what I want to achieve:

I have a RFC in our ERP system that I want to call via webservice (SOAP) from an external system. As the external system is managed by us, the developer of this system might just use the RFCs native input parameters. Hence I would like to skip mapping for this scenario.

Here's what I came up to with (until now).

• In design (ESR) I've created synchronous outbound message interface with the RFCs request message type as output-message and the RFCs response message type as input-message
  
• In configuraiton (ID) I've created a receiver determination, interface determination and receiver agreement.