A number of years ago a mustering type in Queensland lost control and rolled over on take off because he had a bed roll (swag) on the pax seat not secured that rolled foreward and pushed the cyclic over. Personally I had a big guy in who couldn't get the foot operated PTT to work so started stomping up and down with heavy size 14's on the button that did surprising things to the stability, alrming but controllable, other than that I have had numerous time when a pax has bashed the cyclic even with the dual out, to no lasting affect other than laundry costs.