Centaurus,
CAO95.4 lists the exemptions gliders have from CAR1988 and includes
(Exemption from) "paragraph 155 (3) (a), on condition that:
(i) if the acrobatic flight takes place more than 2 nautical miles from a certified or registered aerodrome — the flight does not take place at a height less than 1 000 feet above the highest point of the terrain or of any obstacle on the terrain within a radius of 600 metres of a line extending vertically below the aircraft unless prior approval of CASA has been obtained; and
(ii) if the acrobatic flight takes place at 2 nautical miles or less from a licensed aerodrome — the flight does not take place at a height of less than 2 000 feet above the aerodrome unless the prior approval of CASA has been obtained;"