I'll take the opposite opinion from the group. You said that you were still feeding him twice a day all he wants? Just cut back on his feeding, feed him some in the morning and put him out to hack. During the day, go out with the lure and some food and call him in, and feed him a very small portion and continue to let him fly loose. The only reason, in my opinion, to end the hack is if you think he is in some danger. This bird is an imprint and is not going anywhere, the more time he has at liberty the better he will get.