Thank you for posting. I apologize for the late response.
There are several steps to consider with regard to Central European fonts when converting your FileMaker Pro files.
Filemaker Pro 11 supports only TrueType fonts; fonts other than TrueType used in files created in FileMaker Pro 6 or earlier will be mapped to the closest available TrueType font.
The indexing language for the Ariel CE text fields must be set to the appropriate language, the index for the text fields must be turned on, the appropriate font for the character set applied to all text, and the text entered with the proper input method for your operating system.
The file should be converted on the same platform the data was entered on if possible. If the data has been entered on both Windows and Mac, the conversion can be done on either platform, but undesirable conversion of the data may still result.
If these steps are followed, and the conversion is still not satisfactory, there is a manual process that you can try. This is outlined in the knowledge base article Answer ID: 328 (http://help.filemaker.com/app/answers/detail/a_id/328).
Please keep me posted on your progress.