H. G. Muller wrote on Sat, Jun 28, 2008 07:06 PM UTC:
The logic of FRC castling is that the outcome of the castling in a shuffled variant will be the 'normal' location of K and R, i.e. the one they get by performing normal castling from an unshuffled variant. This could similarly be applied to shuffle variants of games with free castling. Just pick any of the final positions that the castling type with centralized King and corner Rooks could give.