-F option again

I think I have been using -F option since
but now I'm not sure. I either start
with pg_ctl or postmaster directly. In any case
man pages suggest that if you can pass optional parameters
to postgres via -o switch from postmaster. I would
think that if I do it correctly such options will
show up on postgres backend processes. I do not
see such options from top. Below I present
to you relevant snippet of my top output. I've
made sure there is no trailing command line being
cut off due to screen size limitations.

Why do not I see "postgres -F"?

-------------------------
4:44pm up 11 days, 9:12, 1 user, load average: 0.00, 0.00, 0.00
84 processes: 83 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: 0.8% user, 1.7% system, 0.0% nice, 97.3% idle
Mem: 385032K av, 339060K used, 45972K free, 0K shrd, 2152K buff
Swap: 136512K av, 7640K used, 128872K free 100956K cached

PID PRI SIZE RSS SHARE TIME COMMAND
1239 15 900 900 684 0:01 top
14287 15 740 624 548 5:55 /usr/local/pgsql/bin/postmaster -o -F -S 2048
20221 9 5048 4988 4516 0:06 /usr/local/pgsql/bin/postgres localhost httpd what idle