The openacsconfig script appears to want to stick the ACS config file in /etc/opt/openacs/ad.ini. You set SystemURL the same way as ACS Classic. Like ACS Classic, the OpenACS ad.ini file only controls ACS behavior.
Web server-specific stuff all falls under Apache's httpd.conf file (things like whether or not CGI-BIN scripts are allowed, which ports and IP addresses to listen on, the type of access log files that are written out and where those log files go, which server modules are being used, etc.). This is no different than the AOLserver nsd.ini/nsd.tcl config file.
If you're trying to set the IP addresses that httpd listens on but you aren't seeing any changes, trash linuxconf and edit httpd.conf by hand. Good luck.