Obviously the best thing to do is erect a complex series of (JAR approved) screens, similar to a London bus drivers cage, so that the PAX has absolutely no possible contact with any control in the cockpit. Just imagine you weary PAX having a good old stretch and accidentally catches the mixture control, or he stretches too far and accidentally deflects the rudder to full stop.
Christ, doesn't bear thinking about does it? Heaven forbid that he starts sneezing, and accidentally causes the yoke to be pushed fully forward while in the process of wiping his nose......
Common sense......
Cherio
EA