Is there a practical way to demonstrate sustained flight on the back side of the lift curve without an AoA meter?
Flight on the backside of the stallcurve is unstable; any (infinite small) increase in AoA will result in less lift. Less lift will cause the flightpath angle to decrease and the AoA to go up even more. To increase the lift, the nose has to be pitched down, but not so much that the stall is recovered otherwise you wouldn't call it sustained flight at the back of the AoA curve. 

At the same time you are also on the backside of the powercurve. This means that any reduction in airspeed would cause the drag to increase therefore decelerating the aircraft furthermore. 

This double unstable situation would require a lot of fast responses from the pilot, probably causing too high workload. I doubt if it is practically possible to fly on the backside of the liftcurve without special automation.