It doesn't matter how experienced an operator of any type of vehichle is, he or she is not going to be able to push it outside of it's designed performance envelope.
Experienced pilots don't push it past that -- that's the whole point.
Don't think that an owners manual that says "Don't do X" means that you can't do X if you know what you are doing. The world is FULL of examples of being able to do X if you know what you are doing.
The A-20 is plenty capable of aerobatics if you don't go outside the envelope (which, by the way, is a lot larger than for a Shrike Commander, say, that Bob Hoover flew aerobatics in). AH pilots have a lot of experience with staying inside the envelope. But if they push it past here and there and die, they can pop back up again, learning those limits through testing the boundary. Also, in AH, the airframe creaks if it's getting close to failure, so you can (with experience) back off appropriately and fly aerobatics.
If you got some ham-fisted noob trying to do aerobatics in the Shrike Commander (like Bob Hoover), he'd pull the wings off. Bob Hoover did enormous amounts of aerobatics in the Shrike Commander, and it has a lot smaller g tolerance than an A-20.
