help? trouble setting Shared Memory parameters in OSX kernel

hi all,

i've successfully built postgreSQL 7.3.2-STABLE on Mac OSX 10.2.4.

much trouble launching it led me to the discussions
(<http://www.postgresql.org/docs/view.php?version=7.3&idoc=1&file=kernel-re
sources.html>) on setting shared memory parameters -- especially SHMMAX --
in OSX's "/System/Library/StartupItems/SystemTuning/SystemTuning"

so, as instructed, i changed the defaults (near the bottom of SystemTuning):

sysctl -w kern.sysv.shmmax=4194304
sysctl -w kern.sysv.shmmin=1
sysctl -w kern.sysv.shmmni=32
sysctl -w kern.sysv.shmseg=8
sysctl -w kern.sysv.shmall=1024

to:

sysctl -w kern.sysv.shmmax=33554432 # bytes
sysctl -w kern.sysv.shmmin=1
sysctl -w kern.sysv.shmmni=32
sysctl -w kern.sysv.shmseg=8
sysctl -w kern.sysv.shmall=8192 # 4K pages

and defined (in postgresql.conf):

shared_buffers = 2048
max_coinnection = 1024

and rebooted.

unfortunately, immediately after system launch, i still couldn't launch
postgres

eventually, a random check with "sysctl -a" gave:

kern.sysv.shmmax: -1
kern.sysv.shmmin: -1
kern.sysv.shmmni: -1
kern.sysv.shmseg: -1
kern.sysv.shmall: -1

OBVIOUSLY, a problem!

i CAN enter the sysctl settings at the command line, verify success with
'sysctl -a', and then postgres launches/operates just fine .....

QUESTIONS:

any idea why these setting are being written at boot to values of "-1"?

how do i get these setting to 'stick'?

thanks,

richard