you may want to try to use your own body weight to lift the horses weight to the outside. step a little to the outside stirrup and put your shoulder up and back, this will also make your inside leg get put on the horse a little more and it can help the horse almost have to go more to the outside.
When hacking just go around making sure you are not doing it.
Keep more weight in your out side leg, keep outside leg off and use more inner knee and leg to keep from cutting in. Lift up with inside rien. Keep steady contact on outside rien.