mietek81,
Inside of embedded html and css code you can change whatever you like, provided the number of bytes remain the same. Easiest way to keep the number of bytes the same is adding or removing unnecessary spaces, line breaks, tabulators. I give you an example of what I did.
Original
Code:
<body style="font-size: 25px; font-family: sans-serif; ">
Replacement
Code:
<body style="font: 28px 'A-OTF Gothic MB101 Pr6N'; ">
I did not yet try side loaded fonts. I am not sure whether every part of the library knows the path to the side loaded fonts. Don't forget to put font names in qoutes, if they contain spaces.