I think both tricks are useful.
Move priorities ensure that the AI needs not look at all for the extra
moves.
But the bogus square (mine are defined with a position of (-1 -1 -1 -1))
and the verify diminish the value of each add and thus allow more
precision in the points you intend to give.
(For my recent Dual Chess, which uses them both, I also defined several
pieces twice, so that the AI values them according to position, while
identical graphics and the use of the translate command make them appear
similar.)
