The trouble with converted styles is that the instruments don't sound exactly the same on each synth. The ones that were converted by amateurs also often contain errors. There is some info on how to repair and improve Yamaha styles at http://www.1manband.nl/repair.htm

If you have midi files that sound great on your synth you can easily make styles from them that sound just as great. At http://www.1manband.nl/course.htm there is a crash course for this.

At http://groups.yahoo.com/group/onemanbandgroup/ in the file section in the folder "XG styles from midi files" there are a few styles I made that way.

Jos