This question makes me wonder what happens at -1G.
When the load factor of an aircraft increases above 1, the stall speed increases. As the load factor comes closer to 0, stall speed increases and becomes "infinitely" low (basically 0 kts) as an aircraft can not stall at 0G. But what happens at a negative load factor?
For example, during inverted flight the airfoil is still producing lift when the angle of attack is negative (enough). Thus the stall speed should change and as the efficiency of a inverted wing is (almost definitely) not as high, I am assuming that the stall speed decreases.
But is a negative G maneuver necessarily to be done in inverted flight? No!
As a glider pilot, I can refer to negative Gs during winch launches, or rather when they fail. You often practice cable fails, where your instructor disconnects you from the winch. To maintain speed and prevent a stall you push the nose down, ideally flying a small Zero-G parabola (as this will prevent a stall). But what if you push even more? Where is the stall speed going to be at?