Correct joint / "autostruct" behavior:

[HephaistosFnord]

1. When two or more non-decoupler parts are stack-joined together, they should join together into a single rigidbody. The combined rigidbody should have values for maximum shear, maximum compression, and maximum torsion before failure, along with (for each maximum) a 'weakest link' pointer to precisely which part or joint connection will fail if these ratings are exceeded. Ideally these checks are rolled into the standard physics pass.

2. Decouplers and surface attach joins should multi-strut as normal, but with higher rigidity than normal. Rigidity should be increasable (with a slight-to-moderate cost and mass penalty) via tweakable menu, without resorting to additional struts (although additional struts should also stay an option).

3. When a part is repositioned, it should switch to multi-strut (even if it is repositioned off of a stack-join). The multistrut points between the two repositioned parts should ideally be dynamically computed from the intersection of the two part's colliders, unless this would slow the VAB editor to a crawl. 

4. A part or joint that is reaching shear, compression or torsion limits should begin emitting horrible metal-on-metal screeching and groaning noises, like in KSP1's Deadly Reentry mod. Players need rapid feedback that something is wrong and it needs to stop.

This means that a vertical rocket stack won't "wobble" at all, except where a decoupler or docking port joint exists. They will stay rigid until failure.

[Vortygont]

12 hours ago, HephaistosFnord said:

Decouplers and surface attach joins should multi-strut as normal

What do you mean by multi-strut? Is this spring physics or something else

12 hours ago, HephaistosFnord said:

Rigidity should be increasable (with a slight-to-moderate cost and mass penalty) via tweakable menu

It is the same feature as autostrut but with additional resource and mass penalties. I think that body physics must be clear without additional menu

 

[JoE_BoT]

This is

 

 

 

Smort