I am a newbie at kitchen chair cushions, but I have agreed to make 4 of them for a friend. I took the pattern from one of her old ones and tried stuffing it with foam---which was a disaster (the closing of the opening was a nightmare) so I am stuffing it with polyester filling, closure with a small seam, and sewing 4 buttons to hold the filling in place. Now, my question......how much filling do I put in??? Right now I have a nice amount in---it isn't hard or anything----but it is "cushiony". Is that enough??? Will it flatten as it is used??? It looks nice but not as "firm" as her old, used cushion. Any help/suggestions would be very much appreciated.