The SIP RFC (3261) Navigator and clarifier

Hello

I need to add a proprietary parameter in the the contact header of the REGISTER message. Something like
The SIP RFC (3261) Navigator and clarifier

Via: SIP/2.0/UDP bobspc.biloxi.com:5060;branch=z9hG4bKnashds7

Max-Forwards: 70

To: Bob <sip:bob@biloxi.com>

From: Bob <sip:bob@biloxi.com>;tag=456248

Call-ID: 843817637684230@998sdasdh09

CSeq: 1826 REGISTER

Contact: <sip:bob@192.0.2.4>;my_param=1:2:3 <----------------------

Expires: 7200

Content-Length: 0

I want to add this parameter between the UA and the OpenSER.
This is not simple so before I start I want to be sure that:
1. There is no contradiction with the SIP standard.
2. OpenSER will handle it without any patch (actually just ignore this parameter).

Thanks.

Regards,
Michel.