I believe, if the documentation in the newfs man page is correct, 
that you can change the default values for newfs by simply creating a more
complex disktab entry for the disk you want to label.  Then, slap the new
label on the disk and give a newfs on the partitions on that disk.  I
believe there is no code change required.

Someone tell me if I'm wrong.
-Brian
On Nov 30, 10:10pm, Thor Lancelot Simon wrote:
} Subject: Re: More on UFS performance
} 
} Oh -- one thing I forgot:
} 
} If anyone out there has access to a _really fast disk_, like a Barracuda
} or perhaps a RAID 5 system, with a _really fast bus_ on it, like fast wide
} SCSI, on a fast controller (what _is_ the fastest PCI SCSI controller you
} can get these days?  The Adaptec 2940?  The NCR 53C825?), I'd love to hear
} how close our "raw" values (iozone raw /dev/rsdwhatever) can get to the
} manufacturer's quoted figures, or to benchmark values from other systems.
} If the device-drivers or the SCSI subsystem are imposing a "speed limit"
} for some reason, a lot of the logic behind what I've been writing may be
} bogus, or at least we may not be getting performance as good as I think
} we are.
} 
} I hope I'm not annoying anyone by going on at such length about this; I've
} been installing a lot of NetBSD systems in commercial uses and it seems to
} me that the more performance measurement we do, the better off everyone is.
} 
} (that is, _I_ think I have a good reason for blathering on about this, but
}  if y'all think I should shut up, I'll shut up. :-)
} 
} Thor
>-- End of excerpt from Thor Lancelot Simon