i've seen that video before(the full scale one)... i don't think they were really over doing it though.
i thought it was pretty cool to see actually. not many 9 videos out there worth watching.
Based on the looks on those guys faces, they have about as much fun doing aerobatics as one would doing math problems. If I was doing aero like that I would at LEAST crack one of these!! I didn't see one smile. Maybe, deep down inside they knew they shouldn't be doing that with a 9, maybe thats why there is no smiling.
....just about any airplane can do aerobatics....it's all in the hands of the pilot...his/her skill level. The -9 simply has a lower stress design at 4.4 G's instead of 6.
Heck, a Boeing 707 has been rolled as have many Lears and Citations, not to mention the Aero Commander of Bob Hoover.