You'd only need 4 pieces to seal off the corners - one in each corner. They also can't be captured once in a corner, so the only way white would have a chance would be to limit black to those four pieces and force one of them to move.
(hide) If you click on a person's name and then click Finished games you will have a list of games that have been completed, then click on the name of the game to get a summary of all of these games, then click on the name of the game again and you will have a game to view and analyze. (Servant) (show all tips)