Mail 2.1, two PBG4s, Migration Assistant and "Short Name" problems

I need to find an answer to these problems before I go nuts. The
situation:

PBG4 w/broken screen, running an external (duh) Samsung monitor. This
is my shop PB, it's currently masquerading as an immobile desktop.

Identical PBG4 with no problems. Mostly keep at home, but also on the
road.

BOTH PBs have the same dual (Airport/Comcast cable modem for home,
Ethernet/SBC DSL for the shop) network settings, user settings, etc.,
and BOTH receive mail from my Comcast AND SBC accounts.

LaCie 320GB external Firewire drive with OS X 10.4.9 installed.

I wanted a way to keep my work and home PBs synced -- especially Mail
-- without dragging the home PBG4 back and forth. Yes, I KNOW it's a
portable, but as I sometimes ride my bike to work, I'd rather risk the
loss of a $240.00 FireWire drive than an I-don't-know-how-much PB --
plus, the FireWire drive is a much smaller package to carry.

I used Migration Assistant to copy the "home" PB's "Users,
Applications, Network and Machine Settings, Files, and Volumes" (just
like the Migration Assistant Intro says) to the FireWire drive (which
already had OS X 10.4.9 installed), then selected the FireWire drive
in System Preferences as the Startup Disk.

The FireWire drive booted up both the shop AND home PBs just fine, but
I had the following problems:

1. The network and machine settings I had transferred from my "home"
PB to the FireWire drive didn't "take" when I used the FireWire drive
to boot up the shop PB. Neither my home Airport/Comcast cable nor shop
Ethernet/SBC DSL settings were available as choices in the Network
Preferences Pane. To use my shop (SBC DSL) connection while running
off the System on the FireWire drive, I had to manually reconfigure
the settings, always a RPITA.

2. I decided -- probably foolishly -- to try it the other way 'round:
I booted up from the shop PB's internal HD, and used Migration
Assistant to transfer the "shop" PBs settings, etc. to the FireWire
drive. Are you dizzy yet? *I* must have been, because -- just as an
experiment -- I tried booting the "home" PB from the FireWire drive.
Once again, the PB booted up just fine; but once again, neither the
home nor shop network settings were available as choices. As an added
joy, I ended up with a ton of duplicate files and folders on the
FireWire drive, labeled "(from old Mac)" including my ENTIRE 25+GB
iTunes library. Thank God it was 320Gig!

3. I think that one of the problems MIGHT be this -- PLEASE correct me
if I'm wrong:

When using Migration Assistant DURING a System install, IIRC there's
no install-process or Migration-process question about the heinous
"Short Name" (the existence/importance of which I was totally unaware,
though I've been installing Mac operating systems since 1989). Using
Migration Assistant OUTSIDE of the System install process allows you
-- if I'm correct here -- to royally screw things up IF you've already
used a "Short Name" during the install process on the Mac that you
now want to Migrate TO that is different from the "Short Name" of the
Mac you're Migrating FROM. I hope somebody else understands that last
sentence, because I know it's logically and grammatically convoluted.

To me, the importance of the "Short Name" should be emphasized
somewhere, either in the System install process, or in using Migration
Assistant AFTER a System install is complete,or -- preferably -- BOTH.
I had NO idea how important the "Short Name" is to the System, and
while I'm not the sharpest crayon in the box, I'm probably not the
*dullest* either.

Anyway, I'd really like to keep the two PBs synced as regards mail and
new or updated files (and settings), but I seem to have over-thought
(or UNDER-thought!) the means of doing so.

What am I doing wrong here, and what's the BEST way to keep my two PBs
(AND the FireWire drive) all singing the same tune, especially as
regards mail, settings, and docs?

Thanks!

Bart Brown

PBG4
OS X 10.4.9