I'm glad we're not overflowing with admonishments on this subject. I think everyone is aware of the stress category that applies to the 9. I'd rather let individual responsibility take it from there. If someone is deficient enough in both skill and judgment to be at risk of pulling the wings off a 9, then an additional 1.5G of stress margin (6G) is not going to assure their safety.
Regardless of the strength and capabilities of any particular aircraft, pilots will still push them to their operating limits, whether it's a 4.4G RV-9, a 6G Pitts, or a 10G Edge 540. To me, it's all a continuum, and other than legality, 6G's is arbitrary and has no magic when it comes to safety.
You must use good judgment and fly any airplane within its operating limitations whether you're doing aerobatics or not. Plus, the term "aerobatics" is so vague that it could pretty much be anything...and it pretty much is according to the FAA if you look up their definition. So make sure you have the training and judgment to fly any maneuver safely in the aircraft you're in, whether it's a steep turn, a 1G roll, a 3G loop, or high-speed Sean Tucker-like gyroscopics. The inadvertent split-S would likely only happen to the person doing their first-ever aileron roll. And if in this case your instructor is yourself, then there are much bigger problems than just the type of airplane you're flying.
