I know its been done a million ways and for 80 years, but I loathe ANY lock that is internal and attached to the stick/rudder. My thinking, probably wrong, has always been that in terms of extreme gust, particularly from the rear, the loads on the control surfaces have got to be fairly brutal as they try to whip airlerons up or down and rudders left or right, in reaction to those wind forces. Sure, the surfaces can't move much due to the control stick being held in place, but what kind of beating are the actual control surfaces taking?
My other issue with the seatbelt/mechanical internal lock, has been when those methods are used in a manor that results in full UP elevator. What happens when the wind hits from BEHIND and slams into the tail with full up deflection. I can tell you. I've seen the results on others aircraft. $$$.
I've always tried to use external locks for these reason, and home-made when possible. I loved Pierre's idea and the Air Gizmo looks totally worth consideration. Thanks again all!