Solved!  It was indeed a problem with the size of the partition.  Thanks
to those who responsded.

Apparently, the installer will deal with large partitions fine, so long
as you don't ask it to write too much on it.

I re-partitioned to have a 200 MB root, then swap, then the rest usr. 
For my (non standard) admin preferences, I actually have the big
partition mounted on /var and /home a symlink -> /var/home.

So the installer just had to write a handful of directories to the large
partition, and things went pretty smooth.

There were some minor fsck errors when I booted into BSD, but other than
that, things look fine!

The IIci seems to be a stable machine on the 12G kernel so far..  I'm
planning on running Samba and netatalk apple file sharing, so we'll see
how beefy a file server this makes.

Paul Forgey wrote:
> 
> After installing successfully on an LC II, I'm now trying to install on
> a IIci with a 2 GB Seagate Baracude drive.
> 
> Using the 1.1f installer, it bombs 'unimplemented trap' at
> /usr/share/doc/psd/12.make
> 
...