The half-move counter that I added to the FEN is used in frisian games to count the distance to 7 moves draw, so there should be a complete gamestate representation for both variants. I might contact …

I see. It seems that you are already a few steps ahead indeed. However, if you want to be completely correct, there is one additional rule that can make a FEN require additional information for …

Only 7-12 is accepted as the first move, but 27-32 (and then 7-12) wins in the same way.

I have understood this: memorizing the first 10 positions (the squares from 1 to 10) it is easy to improve by counting, for example, from the square number 1, +10 to obtain the square number 11; + 20 …