So following a guide I have successfully setup Kamailio and FreeSwitch together working as an SBC. SIP registration with Kamailio and using FreeSwitch as the media server which in turn authenticates with users in Kamailio. I have managed to pass calls between users etc.

So the next challenge is bolting 2 Asterisks servers behind this SBC and load balancing the media. As the SBC will be public facing I also have to consider NAT which I believe will be configured in FreeSwitch.

I have had some fantastic advice in the past so just interested to get peoples views again.

Thanks. 
--
Keith