I think I've found a solution for the hiding the admin account, but it took a little experimenting to get it to work. At first I had dropped the UID & GID to 102 and along with script: sudo dscl .-change /Users/pgsql UserShell "/bin/bash" "/usr/bin
false" ... it hides the account, but weirdly locks you out at the login screen.

Things seem to be much smoother by dropping the UID to 499 and the GID to 501 along with the script: defaults write /Library/Preferences/com.apple.loginwindow Hide500Users -bool YES

This hides the account well with no problems. I'm still experimenting with a few other things, but this should do the trick.