To Mark Thompson: three always is a good number. We have so much possible
positions in CRC, so it does not hurt to skip some to avoid any conflicts
with Gothic Chess. Live and let live.
To Fergus Duniho: it seems as if you would use a very complex method to
detect invalid starting positions. I will add a more simple method in
short to the reference code I have posted here yesterday. Thus one will be
able to see, that generating valid CRC positions only is neither a run time
problem nor too complex to be programmed.