Hi! Please try our very recently updated and improved "Create 2D/3D Hinge Chain" functionality, it creates a more sophisticated physics rig which should solve your problems. The updated feature is available in the latest 3.8 and 3.9 unitypackages here:
Spine Unity Download
There is now also an example scene that demonstrates a working cape setup using these generated hinge chains, it can be found under "Spine Examples/Other Examples/SkeletonUtility Platformer HingeChain Physics".
There will also be a blog post about it soon that demonstrates the updated feature, but I assume you will figure it out anyway. Just be sure to adjust the drag and angular drag values at the generated Rigidbody
objects to achieve the desired weight effect.