GT's response above makes a good case for the rods not needing to flex. I would, however, like to understand where the 7.5 degrees/15 degrees specs came from. If you have a torque machine, then by all means test one as regardless it will be good for us to know.Torsion in the axle rods?? I am not following this thought. They are refereed to as torque rods not because they are in torsion but because they are installed to resist the torque of the axles from pulling and stopping since the springs do not assist in those matters. the only time they MAY be in torsion is during severe articulation of the rear axles when the transverse movement has exceeded the motion in the rod end and rubber bushing.
FWIW the old or original rods were round, on both 2-1/2 and 5 tons.
I have access to a torque machine if someone really esponse ewants to compare the torsional characteristics of the rods. I agree that it would be good information for comparison, but respectfully disagree that the stiffness of the "torque rods" will have any impact on operation of the rear suspension. But that being said, I am most willing to listen to other opinions.
Extending rods is still potentially hazardous due to having modified a suspension component without proper validation testing.