[Serusers] SER with internal/external interface

I am trying to setup SER so it can be used both by internal and external users. I have tried to set it up with two interfaces, one internal and one external. There is a STUN server setup for external users as well. The problem with this is that internal clients will obviously add a VIA header with their internal IP so if they call someone on the outside and that someone sends a BYE for example, it never gets to the internal client because it tries to send it to the internal IP address. Putting SER completely on the outside does not work either unless all NAT-ed clients support ICE (because there is no sound coming through). The only client which I've seen to support ICE so far is Xten's Eyebeam softphone, but I'd like to be able to use hardphones as well. Does anyone have an idea how to accomplish what I need to do? Is there something I can do in ser.cfg so the VIA header of the internal client is stripped, or can I have 2 SER's, one listening on internal IP and one on the external IP and have them relay each other? I have tried the mhomed directive but that seems to mess things up even more.