This is probably a little bit irrelevant as it's a MkV, but it clearly shows what happens when the negative G cut outs occur.
If you watch and listen closley you can hear the engine misfire and see the smoke (especially when he's inverted). It happens quite a few times. Just thought it was interesting.
Alex Henshaw flight testing a MkV at Castle Bromwich 1941. (ignore the terrible acting bits!)