[Serusers] Assymetric RTP and Symmetric RTP

I guess this is the proper terminology I am looking for. I have an Asymmetric UA and an Symmetric UA that I amtrying to connect through SER and Mediaproxy. The Asymmetric UA does not register, rather it is on the LAN and is completely accessible to SER. The Symmetric UA however is on the internet and would likely be going through a NAT--hence the need for SER. The problem that I am having is that SER and Mediaproxy are ignoring the SDP info from the Asymmetric UA and sending the RTP stream from the Symmetric UA back to the same port that the Asymmetric UA sent from. Any ideas on how I can get Mediaproxy and SER be selective about how it sends the RTP stream to the unregistered Asymmetric UA? Thanks again. George