After all, the perfect barrel roll is only a 1G manoeuvre.
Not quite, you need to pull up into it
I'm sure you could roll a 172 (flying through the wake of an A320 nearly did it to us once).....but you'd be a bit stupid to do it deliberately....the 172 is NOT APPROVED for aerobatics. When it goes tits up and the wings fall off, remember this on the way down - just hope these people don't take anyone else with them.
In one of the aerobatic books I have got, it has a nice diagram of an aeroplane at 60 degrees nose down with 17 second (I think) written beside it. This is the time till impact at 120kts (I think) at 3000'. It also has a pic of one in the vertical with something like 12 seconds written beside it......
One thing I didn't know before starting to learn aeros is that in a roll (not barrel), in a typical aeroplane (without symetrical wing), the nose will drop approx 60 degrees, which is why you pull up 30 degrees before you start the roll......