SMIRF Engine: Well, I try to translate and extend (German readers please forgive me ;-) ): As far as I know, the autor of Winboard_F is working on the support of several variants. Generally the differing castling rules are one main problem. SMIRF is able to follow several of those castling methods - thus other people surely also will be successful with that one day. The best option would be to ask the writers of those new Winboard extensions and 10x8 engines themselves for details.