Their custom keyboard designer does let you enter extended characters from the fonts they allow, like Arial, Wingdings, etc. That does allow you to enter Arial vowels like alt-0234 ê, and áéí, . Also the š and ý are in the Arial second half. no clue if the c, r and z versions exist in any of their standard fonts though. Whether they actually print them is another matter only they can answer, but I got a wingdings extended character printed by them without any stress.
