Small-Scale Snicker Snack

5th level: vorpal effects small creatures or smaller,
and the bonus dmg increases to 2d8.
11th level: the sword becomes a +2 magic weapon,
vorpal affects medium creatures or smaller, and
the bonus dmg increases to 4d8.
11th level: the sword becomes a +3 magic weapon,
vorpal affects medium creatures or smaller, and
the bonus dmg increases to 6d8