[Users] privacy=full and contact hf

Hi, before forwarding a call (INVITE) from the PSTN with flag "privacy=full" in the Remote-Party-ID hf to a none-voice-licensed carrier I need to make sure that the calling party number is completely wiped out from the SIP requests. I see this number at three places: the Remote-Party-ID hf itself, the The Remote-Party-ID hf can simply be dropped or replaced by something anonymous. The From hf can be rewritten using uac_replace_from. But what about the Contact hf? This field is, as far as I can see, required for routing purposes, to tell the called party side where to send replies. So, if I would manage it to rewrite the field, I would have to make sure, the replies sent to the rewritten address once again will be rewritten to target for the meant destination. Is there a best practice for this item? Thanks, Wolfgang