Overblows can be bent up. Some people can play enormous intervals on just one overblow. The tonal quality is difficult to maintain and the further the note is bent up the more difficult it gets. However with practice the tonal quality can be improved and the notes can be of practical use. Especially when played as part of fast embelishments they can be helpfull by eliminating the problem of fast switches in breath direction.
The following examples are played starting from the bent up overblow down to the unbent overblow (or overdraw in holes 9 and 7).