Transliterating th

On a whim I decided to alter the transliteration scheme of Skerre.  I
decided I wanted to eliminate digraphs for single sounds.  Here's what I
have devised so far:
Sound    Old transliteration   New     Natlang precedent
/S/            sh                          x        Old Spanish
/x/            kh                          q        None, just a
correspondence with q and /k/ especially in Romance langs that lends itself
well to /x/ in my mind.
Yet I'm stuck when I get to /T/.  I would prefer to use an existing letter
of the Roman alphabet since that is easy to utilize with the computer.
However, in my mind no letter really works. The letters that are already
taken (besides those mentioned above) are a, d, e, g, h, i, j, k, l, n, o,
r, s, t, u, w (all corresponding to their IPA values, incidentally).
As I type another idea crosses my mind.  In some travel book I saw one time
(which I admit aren't the most linguistic of books), they used the numeral 3
for /T/ since three begins with /T/.  I imagine this could be a problem if I
also used numerals in text, but I've translate so little into Skerre that
it's never been an issue (at least that I can remember).  Any thoughts on
borrowing this idea?

-Doug