Messing around with systems in flight????
Remember the DC-4 (Air Pennsylvania, I believe) in the 1940's???
Check pilot engaged the gust lock during cruise @ 4,000 ft. The aircraft started to climb, the Capt added nose down trim, Ck Pilot disengages the gust, and voila...the first half of an outside loop...A CAA (pre-FAA) Cessna was behind the flight and witnessed it....
60+ yrs later and we still haven't learned...