[XeTeX] XeTeX hyphenation support for supplementary chars?

[Kenneth Reid Beesley]

    XeTeX hyphenation support for supplementary chars?

I'm typsetting large documents in supplementary characters, in the
Deseret Alphabet (U+10400 to U+1044F) to be precise, and my only remaining
problem is hyphenation.

JK previously suggested that I'd need to define \lccodes for the Deseret
Alphabet characters, so that patterns could be defined, or so that \hyphenate
could be effective.  It took me (not a TeX guru) a while to understand that
\lccode is used both for lowercasing and for hyphenation control, but
then I found
the following:

"About XeTeX", Jonathan Kew, 17 Oct 2005

"Because XeTeX works with UTF-16 code units, TEX commands that deal
with character codes, such as \char, \catcode, \lccode, etc., have
been extended to handle 16-bit values (up to 65535, or "FFFF). Note
that it is not possible to assign individual character properties such
as \catcode to non-Plane 0 Unicode characters, because these are
treated as a pair of surrogate codes; however, there is probably
little reason to need to do this. Supplementary-plane characters can
still be treated as normal text to be typeset. "


"XeTeX, the Multilingual Lion:  TeX meets Unicode and smart font
technologies", Jonathan Kew, TUGboat, Vol. 25 (2005), No. 2.

"Hyphenation support:  Along with other character-code-oriented parts
of TeX, the hyphenation tables in XeTex have been extended to support
16-bit Unicode characters.  This means that it is possible to write
hyphenation patterns that use any (Plane 0) Unicode letters, including
non-Latin scripts as well as extended Latin (accented characters, etc.)"

Taken at face value, these statements would seem to indicate that
one cannot define \lccodes for Deseret Alphabet characters (there is
an uppercase/lowercase distinction in this alphabet) and that one cannot
define hyphenation tables over supplementary characters.

Am I stuck? or am I missing something?

Thanks,

Ken