@kartu, I wonder if I could ask for your help?
First a bit of background...
I have just received my PRS-T1 and am playing around with the fonts. Whilst the included serif fonts (Amasis, Palatino nova, and Really No2) are not bad at all the implementation appears to be poor. Bold and/or italic text seems to be mostly (but not always) changed to regular if you try to use any of the 3 included serifs.
I am a big fan of PRS+'s font capabilities and the PRS-T1 is definitely a step backwards for anyone who is used to using PRS+ for font customisation.
I haven't finished testing yet but the retention of italics seems rather random. There may be a predictable pattern but I haven't found it yet. So far, Bold and BoldItalic have always been lost.
[Edit:]occasionally Bold is retained in headings
[Edit2:]Having done more testing retention of bold and italics seems to be completely random unless you select font=Original
There is better news if you want to manually embed fonts. This appears to work but of course takes manual effort. I've only tried one epub so far.
Now, finally, for the help...
I know the PRS+ method of having both customised fonts and css on the device will not work but I thought I'd try the old halfway-house method of storing the ttf files on the device and adding the @font-face css to each epub. So far this is not working. It may well be that the old internal memory root location actually being res:///Data is no longer correct. I am wondering whether you know what it has changed to?