Hi Les

: 2. Lengths of 1"x1/4" ally at a foot or two may feel
: stiff when you try to bend them by hand
: but in reality it is not stiff or strong and once an axial twist
: has started it rapidly becomes even weaker!
That's true but it's not the cradle's job to prevent axial twist. The tethers do that. The cradles were not the issue - the issue was that the crosswind force exerted so much force on the rack (through the cradles), that it sheered the bolts holding the cross bar to the roof rails. A front tether from the bow down to either side of the car would have all but eliminated this force.

All a cradle really needs to do is to hold the kayak to the crossbars - this doesn't require it to be especially rigid (at least not more than aluminium or plastic would provide).

Regards, Ian