Sumerian: Welcome back!

The castling is the same, the King moves three squares towards the Rook and the Rook is placed on the other side of the King. Maybe for your program it is a problem since your Capablanca Random Chess set up will pretend the Kings are on the "f" file so that in CRC the castlings will go as defined by that game. I suppose your mirror image game is the same as far as that goes. Perhaps you could just add Embassy Chess to your program as you did for Janus, Bird's, and Capablanca Chess?