Hi Luca, as far as I know the Windows calls that MoI uses to retrieve the font outline information only work with TrueType fonts.

So for an .otf font, you may need to convert it to a .ttf font instead in order for it to work directly with MoI, it looks like there is one converter for that here:
http://www.fontlab.com/font-converter/transtype/

It is possible to sift through the font data files more directly rather than using the Windows function to access the font information, but unfortunately that is a major step up in complexity and not easy to deal with.

- Michael