Vertical text alignment with AttributedString and embedded TTF font

I use a AttributedString to show a file path while using a embbeded TTF font. I want to draw the file extension with a smaller font, so i append it to the AttributedString object with the same font but different height. On OSX it looks as expected but on Windows it doesn't. 



Any suggestions to fix that in Windows?

Did you ever find a solution to this? Setting a certain range of an AttributedString to a smaller font seems to cause the smaller font characters to be incorrectly aligned to the top.