So far I have seen there is no method to change the rate of chars written. Only mouse speed can be adjusted.
You could use http://ini4j.sourceforge.net/ too. Pretty simple. Works like a charm.
public static void setIni() throws IOException
{
Wini ini = new Wini(new File(Data.ini.getAbsolutePath()));
ini.put("Settings", "Version", Data.MAJOR_VERSION + "." + Data.MINOR_VERSION);
ini.put("Settings", "Theme", "org.pushingpixels.substance.api.skin.SubstanceGraphiteGlassLookAndFeel");
ini.put("Settings", "Download", Data.DOWNLOAD_FILES);
ini.put("Account", "Username", "");
ini.put("Account", "Password", "");
ini.store();
}Something I made a while back. Perhaps you could use something of it and have a example.