Even small flexability may give the starting point for high frequency movement which may swing up into heavy flutter.
Do not underestimate the forces in a swinging system.
I am pretty sure the horns DUP recommended will be safe, and sure the prepregstuff will be reliable aswell but for me there is no need to split forces into bending forces and torsion forces when there is the option to reduce it to just bending forces which are easier to controll.
This is for sure a more or less theoretical discussion, it is obvious that there are lots of nice working balljoint linkages out there.
But its not the way an engeneer would design!