sysinst, serial console on soekris

I've been using a NetBSD/mac68k box as the internal router on my home network
for several years, but I think it has finally run out of steam.  I'm in the
process of replacing it with a soekris 4801.  This is my first i386-based
install, so I have a couple of questions.

To paraphrase/distill advice from various mailing lists, "all I need to do" is
to pxeboot via tftp, then boot the install kernel over NFS, install via
sysinst, and select a serial console.

I have pxeboot and the install kernel booting with no problems.  My question
is about getting the serial console set correctly (I don't see what I'm
looking for in the INSTALL docs).  Is sysinst going to DTRT on it's own or ask
me if I'm using a serial console?  Or do I need to drop into a shell and run
installboot after the installation is done (and before I reboot)?  As I recall
from my last install on mac68k, sysinst leaves things so that only console
logins are possible (i.e., ssh is either not enabled yet, or root logins via
ssh are disabled; I don't remember which, just that network login by root is
disabled), and I don't want to find myself with a fresh install and no way to
use the 4801.  I'd like to get it right the first time.  :-)

Thanks,
Mark