Aerobatic base height
In Australia a pilot with an aerobatic rating must not do aerobatics below 3,000 feet without a waiver.
About 5 years ago the CASA draft of Part 91 proposed 1500 ft however the response they got from the Australian Aerobatic Club and others was summarised as "Many respondents indicated that the minimum height for aerobatics should be initially set at 3000 feet and not 1500 feet as proposed in the regulation."
I haven't taken much interest in Parts 61 and 91 for ages due to the rate of progress but I believe that 1500 ft is now back in the draft.
As Pogo said, "We have met the enemy.... and he is us".