Is it possible to set up a pool with pushpool and have it connect to another pool (e.g. slush's) by specifying the connection details for that pool rather than the bitcoin RPC details in the config file? I have what I think should be the right setup for this, and pushpool isn't making any complaints, and appears to be getting the right responses from slush's, but slush's isn't showing it as having connected. Am I just making a mistake somewhere, or am I missing something fundamental?