Dick Arentz cites a 33% solution as opposed to the B&S 25% solution. I would say go with what Arentz says, it is no use wasting prints to save a few cents on PO developer.

BTW, just to make sure, that is 33 grams of PO to make 100 ml. Or IOW 330 grams of PO to make one liter. Notice I said to make 1 liter that is you add water to the powder until you reach the 1 liter mark, you do not add 1 liter of water to the 330 grams of PO.