Going back to the Hood Flap for a moment ... I have a very vague recollection of a reported incident where a RAF Chipmunk was in a Flat Errect Spin and when the crew decided the best course of action was to leave the aircraft (normal recovery actions were ineffective apparently) ... the mere operation of the hood flap and subsequent opening of the canopy ... the aircraft recovered, the crew then stayed with it and recovered back to base safely.
Not sure about this happening to a Chippy, but it definitely happened to a Bulldog in t the early days of it's service. The crew jettisoned the canopy and the aircraft recovered due to the large canopy blanking the rudder.
Beags - I had heard this while flying the Chippy, but never heard it confirmed. It's possible with the introduction of 100LL, but the Gypsy has such a low compression ratio, I can't believe it would have changed the risk of detonation or valve seat erosion. I suspect it was after some carb icing events.