How can I send aaa traffic from my PIX506E to our ACSServer and SNMP traps to our monitoring station through a VPN tunnel?

Do I have to add the server with interface outside (like: aaa-server CiscoACS (outside) host ACSSErver)

and add the outside interface to the access-list for the VPN traffic.

Can't I use the inside interface because our outside interface has a public IP address and that will be difficult to settup on the ACS Server?