strike-through text in enriched-mode

[billy]

Hello all,
I need to create strike-through text and save it in a file using
enriched-mode.
It seems like an obvious task so maybe I'm over-looking something, but
here's where I'm at:

in my .emacs,
(defface strikethrough '((t (:strike-through t))))

This works, I can access it with M-o (O)ther, strikethrough. But it
only sets the face for the current buffer, enriched-mode won't save
any meta info.

I'm unsure of how to access enriched-mode definitions in my .emacs, so
I poked around in ./emacs/lisp/textmodes/enriched.el,
In (defar enriched-translations), I added my new face "strikethrough"
but it would not save out.  tried creating a new defface in that file
but that didn't work either.

What I eventually did just so I could keep working was to change the
defface "excerpt" from (:slant italic) to (:strike-through).
I know this is a horrible way to do it so I'm looking for a little
guidance.

Also, how do you change the key binding for this face to something
like M-o (S)trikeout?
Thanks in advance.