DG,
The Hunter was not cleared for inverted spinning in the Release to Service. The Boscombe Down Hunter T7s had a specific clearance for inverted spinning (and erect spinning and stalling) based on having cockpit displays of AOA and lateral stick position plus an audio altitude alert system. In addition, for inverted spinning a safety pilot had to be present in the telemetry ground station. I could go on but that would be thread creep!