Hovering a plane on the prop down, if possible, should be very much harder than hovering a plane conventional style. When hovering planes conventional style, the force is above the CG and therefore already helps it to a natural occurence, and we build our planes with extra large control surfaces with extra much throw, to be able/make it easier to maintain the attitude of the plane.
When standing a plane on the prop, and maintaining that attitude, the pilot would have to be so super observant and fast with the controls, that I still have a hard time imagining it possible. The airflow in front of a prop is nothing like the airflow behind it, when airspeed is nil. Perhaps if a huge, slow turning prop, much like a helicopter rotor, were used, at least the gyroscopic forces would be on our side.
DKjens