Fast RFC - How to enable?

I have a Java servlet that is being deployed in the J2EE stack on the same system that is running the ABAP stack. When the servlet connects to the ABAP stack on the same system, the JCO Client attributes indicate that the connection type is always a '3' (R/3 connection), and not the 'F' (fast = shared memory pipe) that I expect. I don't see any mention in the SAP docs of any explicit steps that I need to take in order to enable or use fast RFC. Even though it is not officially supported, I tried to explicitly set the jco.client.type property to F before making the JCO client connection, but this didn't seem to help. Any idea how to control whether fast RFC is used?