Adding nice to an rc.d script

[AGC <agcarver+netbsd%acarver.net@localhost>]

I'm trying to figure out how I can add a nice command to daemons started 
by rc.d so that I can adjust system performance a little bit.

Specifically I want to start by raising ntpd's priority to -5.  The 
built in priority command line optiosn of ntpd (-N or -P -5) don't seem 
to be working when I add them to the rc_flags variable in the precmd 
function.  Top says priority is still zero.  Manually running ntpd using 
nice -5 does work so I'm trying to incorporate this into the startup 
script somehow.