Your list looks ok.
Running two separate versions is pretty straight forward. You need to run each version with its own install directory, its own port number and its own data directory.
I currently run two versions by having them installed under different user accounts with environment variables (PGPORT and PGDATA) set to a different port number and location for each version.
Don has recently added a change to the pg driver, so that the pg installation directory can be specified in your nsd.tcl file. You could then build each pg version with the port and data directory already configured which would allow you to run multiple pg versions from the same user account without having to set environment variables. Changing versions for a particular openacs installation could be done by editing your nsd.tcl file.
