More than a pawn: I think "two bishops" was about right. The value of each stone (as an ability to stake out territory -- sometimes called the "temperature of

More than a pawn: I think "two bishops" was about right. The value of each stone (as an ability to stake out territory -- sometimes called the "temperature of the board" in game theory) decreases as the game goes on. A stone in each corner is huge, probably worth about 80pts of potential territory. In the middle game, the temperature might drop from 20pts to 10pts per move. So your averaging method doesn't quite work. :)