Only ever tried it ( only when a solo QFI ) inverting and slowly reducing speed to just before the stall, then applying full rudder, stick fully forward, but with ailerons neutral and trying both full aileron in both directions it just fell into a sort of wallowing spiral with the speed increasing. I guess it was not truly stalled.
Some time later I was walking through the hangar and saw a JP with the fin root fairings removed, revealing the three small bolts holding the fin on, made me very conscious of fin loading, never tried inverted spinning again.
Thought flicks on the JP were always banned, certainly since I first flew it in 1962, 3s and 4s.
Happy days!