Hello Ron,
Sorry about the confusion on the word "tough". In the industry, I was an aero engineer with North American Aviation for 35 years, the phrase "tough bird" meant strong, didn't break easily, and kept flying after heavy damage. The 15 flys very easily and I can say that having flown 19 different types and 42 different sailplanes. No high performance birds I might add. The ailerons can get very stiff but there is a cure for that however.
I want to say, the only reason I took acro training was to get comfortable with any "other than normal attitude" situation that I might encounter flying the wave (rotors can be nasty) or very strong thermals sometimes found in the southwest USA. I had no intentions or desire to become a "stunt" pilot at 63!
After completing 13 flights with Las in a Grob Twin Acro (basic course) I did inverted flight,aileron rolls,single & double,immelmans,Cuban-8s,wing overs,wing tip vertical 360s and 720s and several loops in the 15. One day I did 4 or 5 continuous loops while still at Estrella with Las observing from the ground.
None of these are that difficult,with proper instruction, and gave me knowledge and comfort as to how to handle the situation if I found myself up side down unexpectedly. A smooth steady hand is also VERY important. I had a g-meter on the panel and I paid attention to it! I did a few more maneuvers for the next few months after I got home and then that was the end. I then flew the 15 mostly on the ridge in Tennessee, USA.
The 15 can do many acro maneuvers but it is NOT fully aerobatic by definition. Things not to do, a true stall turn,tail slides,snap rolls or outside loops.
I'm sorry I got a little wordy but there just was not a simple answer without cutting you off. If you would care to have more discussion I think we ought to take it off the Forum so we don't spam the members. :-)
Regards
Gale