Mark,
You may port forward 443 to 443 on the UC500's wan IP. You could also forward a port other than, say 11443, to 443 on the UC500. You may connect either with CIPC and a computer that is VPN connected or with a spa525G2 phone via SSL VPN. If using a port other than 443 you will have to specify it at the end of the spa525G2 connection target IP address (0.0.0.0:11443). The SSL VPN tunnel should be a full tunnel.
Configure these options on a remote spa525G2:
1 username
2 password
3 public IP address of UC500 gateway
4 enable alternate TFTP server
5 set alternate TFTP server to be 10.1.10.2
6 disable CDP and LLDP autodetect
7 set call control to be SCCP
I apologize but the 7900 series phone VPN is not currently supported on UC500.
Hope this helps,
Christopher