Thanks Ujwol, renaming arcotcommon.ini did indeed allow data source modification during risk install.
There were few more steps needed for a successful service installation and start..following
1- Stop Strong Auth (Strong auth was installed successfully with datasource configured to use non-standard DB port)
2- Rename arcotcommon.ini (This allows DSN entries modification during risk install)
3- Run Risk installation without primary DB initalization & service starts
4- Provide exact DSN values as provided during strong auth & test connection
5- Complete risk installation
6- Logon to DB and run following queries
db-config-for-riskauth.sql";
db-config-for-riskauth-table-index.sql"
7- Rename back to arcotcommon.ini
8- Start services