Hi guys- I am getting a little uncomfortable with where this thread is heading. As far as aerobatic aircraft certification is concerned, it is not simply a matter of G-limits. Aircraft in Acrobatic category also have to have demonstrable safe and predictable spin-recovery behavior, and the manufacturer will specify what maneuvers can be done safely.
For instance, the Decathlon is certified in the Acrobatic category, however, tailslides are not approved, you could potentially damage the aircraft trying to do one.
Some existing "grandfathered" types like the clipped Cub are very capable aerobatic airplanes and fall into Sport Pilot eligibility. That does not mean they can do anything, but they will recover from a botched maneuver safely. Current manufactured LSAs (which seem to be proliferating rapidly) do not have an Aerobatic category of certification, basically the manufacturer states which maneuvers are approved based on whatever criteria they are comfortable with. For instance, the Cessna 162 Skycatcher is certified as an LSA but is not approved for spins (apparently with good reason).
If you want to do aerobatics as a Sport Pilot, there is absolutely nothing stopping you, you are subject to the same restrictions as any higher-level certified pilot. There is no specific aerobatic certification or endorsement. However, just because an LSA-compliant airplane has a +6/-3G limit, it may not be safe for aerobatics due to unpredictable spin or loss-of-control behavior.
My bottom line on this- if you want to do aerobatics as a Sport (or any other) Pilot, get some formal training from a qualified instructor (the IAC is a good place to start, check their website through EAA), make sure the airplane is truly safe to fly aerobatics, and follow the safety rules (airspace,altitude, parachutes). DON'T try to teach yourself, DON'T do aerobatics in non-aerobatic airplanes, and make sure you have had some good spin training.
Then (and only then) go out and have fun with it!! Cheers, Tony