Chris,
I think I may have figured out the confusion you and others have with the 2/4 point. You are confusing the point to be a line. 5B7.1 Lines; All aerobatic manoeuvers are started and ended by a horizontal line of recognisable distance. When you roll to inverted and fly inverted the same duration as knife edge this is a point not a line. If after flying inverted the same duration as knife edge you fly a little longer then that becomes a line and you should be docked 2 points, as is the case if after the full roll you fly a line before you push to the outside loop.

Hope this helps you and others to clear up the confusuion.