I am just thinking it over, whether to support also free castling in SMIRF - the variation, where the King makes at least two steps, to enable an unambigious move entering via a GUI. Then a lot of other chess variants would be able to be supported. But there is a question left: how is the regular notation for those castlings? O-O and O-O-O would not at all be sufficient here.
SMIRF is downloadable at: http://www.10x8.net/down/SmNewSetup.exe