dealing with vietnamese fonts

[querty]

Hi all
I hacked my PRS 505 with the vienamese unicode fonts (UFT-8)
when I save a txt file coded in unicode uft-8, and put it directly in the reader, every thing is ok . But this way I can't have the cover and the author's info.
So I try to convert it to epub with calibre. The text never show in the right letter.
I even tried to convert from HTML, no sucess.
I 'd spent 2 nights trying every step, searching all the forum, some time reading a lot of codings coming from Mars. I must miss something simple in the setting of calibre.
So please, I need a great help...