MULE-UCS and font-encoder ?

Hi all !
Does anyone know how to enable UCS font-encoder feature in xemacs ?
I have tried following in my init.el :
---------------------------------------------------------------------------
(put-charset-property 'latin-iso8859-1 'x-charset-registry "iso10646-1")
(put-charset-property 'cyrillic-iso8859-5 'x-charset-registry "iso10646-1")

(set-face-font 'default "-*-arial-*-r-*-*-*-200-*-*-*-*-iso10646-1")

(set-charset-ccl-program 'latin-iso8859-1 'unicode-font-encoder)
(set-charset-ccl-program 'cyrillic-iso8859-5 'unicode-font-encoder)
---------------------------------------------------------------------------
But xemacs still load iso8859-1/iso8859-5 fonts for text output

xemacs-21.4.12
mule-ucs-1.04