Restraining flight controls at the control stick/wheel is a last resort, always try to use external control locks. The flight control system is not designed to withstand unquantified gust loads while parked in strong winds. If the cockpit controls are locked, yet the flight controls unrestrained, they try to move against the control system as a whole. When something gets damaged in the flight control system, it may be very difficult to detect during a walk around inspection. I have twice taken off in an airplane, whose walk around was fine, but actually had damage, Both times, it affected the way the plane flew in a very unsafe way - which I found out only in flight. I now know what better to look for for defects, but the first thing I want to do is remove external locks. The most serious such event was an Air Moorea Twin Otter, flight 1121, easy search. The plane spent a lot of time on the apron with cockpit locked controls, downwind to jet blast - the elevator controls failed in flight.
If you can't install external locks on all controls, at least turn the plane into the prevailing wind....