And there's another detail that all of us forgot! When the crooked bishop
is on the edge of the board, one of its paths in the (0,2) direction is
blocked, even though the (0,2) square might be on the board.
When I included this in my evaluation, I got the result that the crooked
bishop has about 1.2 times the mobility of a rook for a broad range of
reasonable values of the magic number.