How to make fixed joints less wobbly?

Hey, I am creating a sandbox game and found that fixed joints are too wobbly to act like real metal channel:


I want to make the joints stiffer and less wobbly; but since I still want a little flexibility, I can’t use hierarchy parenting all the parts. I also tried configurable joints, locking all the motions, but it’s acting exactly like fixed joints, and once I switch projection mode, the Physics start to act unreasonable.

What are my options? How do I make a tighter joint?

Feel free to give APE (https://forum.unity.com/threads/ape-deepmotion-avatar-physics-engine-for-robust-joints-and-powerful-motors.259889/) a try.