I've used CJK.ttf to overwrite Serif_Bold.ttf, Serif_BoldItalic.ttf, Serif_Italic.ttf, and Serif_Regular.ttf on a DXG, following the instructions in
a reply posted here. Chinese characters now display ok without a hitch, but it seems that CJK.ttf doesn't support Latin diacritics very well. Acute and grave accents (à ì é and the like) in one book look ok, but umlauts (ä ö ü etc.) in another appear as blank boxes. The fonts used in these two books seem to be different though. I've attached screenshots of the two books in question.