where does the -i go?

I've seen there are multiple ways of doing the -i for postmaster.
Someone said something like: Uncomment #PGOPTS= -i Iv'e also seen it
in the postmaster call e.g. postmaster -i foo

Do I need to add it to /rc.d/init.d/postgresql in the line below?
Where?

su -l postgres -c "/usr/bin/pg_ctl -D $PGDATA -p /usr/bin/postmaster
start >/dev/null 2>&1"