It should be possible with a sufficiently powerful aircraft, given that knife edge "level flight" is easily doable in, say an, Extra 300. Absolutely no chance in anything less.
There's one stunning video clip I've seen where Jurgis Kairys does a low pass, knife edge. The video is taken, 50ft or so above ground, from a grandstand at racetrack in Japan. He passes *below* the camera position.
Forward airspeed is very low in these scenarios, as the aircraft is partly 'helicoptering' (aka 'prop hanging'), rather than flying on the fuselage & rudder alone.