Fixing (scsi) drives at particular /dev locations

[scion+fbsdq at webrelay.net]

FreeBSD 5.2.1; Sun/Cobalt LX50; GENERIC kernel

Greetings,

The darned LX50 is wired with the first SCSI bus out the back,
and the second toward the builtin drives.  So, upon adding an
external drive, the internal drives all renumber with the generic
kernel+device hints.

I thought adding a line to /boot/device.hints might work, so
reading /usr/src/sys/i386/conf/gethints.awk for clues, I added:

	hint.da.0.at="ahc1"

But that didn't have a noticeable effect.  Looking again, I probably
asked too much from that interface, as I see no examples with ctlr
name+numbers to the right of the =.

So, how to fix device 0 lun 0 on ahc 1 to be da0?

Alternatively how to get /devfs to incorporate the ctlr number in the 
/dev entry, like: dac1s1a?

Thanks,
-sam