I guess the 24mm aluminium screw is just supposed to be "tight"?
The workshop manual says to torque everything according to the torque specs, but obviously these specs are not in the workshop manual - go figure. #3 is the one I'm referring to.
Big thanks for this - I actually came to the 55Nm torque value by unscrewing the bolt with a torque wrench. Clicked at 55Nm, and turned at 60Nm, so It's confirmed. Finally, I can get the rearsets mounted.