[SR-Users] media between 2 clients behind separate NAT

Hello, When I have 2 clients using a kamailio proxy, and both of the clients are behind their own NAT, then my only options for relaying media between them is using some kind of intermediate rtp proxy or STUN etc? Proxy is on a public IP and essentially I am asking if I can avoid setting up stuff to proxy the media or mess with STUN, by using some kind of request response mangling. i.e. have both clients's sdp address/port changed to their public facing ip/port and then each client can send an initial packet to the other end. Those initial packets will be blocked by the other receiver router, but they will open a nat hole so that next package from the peer will pass through. Is that feasible? Thanks.