I think the problem with using stuffing for 10" squares would be that the stuffing would tend to ball up over time, making the puffs lumpy. Nylon stockings would be ideal for this situation, as you could baste them into a squarish shape so they don't move around inside the puff. A layer of Hobbs PolyDown would be a lot easier, though; just cut to size. If there isn't enough puff, you could add another smaller layer on top; just baste the two layers together so the smaller piece doesn't move around inside the puff.