UIB encoding... hmmm....
The only people I know who have experience in it (that is: the 'MS Windows format') are Patchou and somebody else who I forgot the name of, and I even think TheBlasphemer (oldie from here too, though he is not active anymore). But Patchou doesn't develop Messenger Plus! anymore. Nevertheless, maybe, if he reads this, he can give you some pointers etc.
Messenger Plus! is currently developped by Yuna. And I dunno if they will give you some pointers or not (you know: 'trade secrets' sort of
). But who knows......