Should actor massScale affect all aspects of simulation?

[Qriva0]

Instead of applying a force to one particle/part of the object and attempt to use infinite temporal resolution to propagate it faster, a much simpler and accurate solution is to just calculate and the end position for all points in the object yourself: Eg. if you must move an object from position/rotation A to position/rotation B, derive the position deltas required to take every point in it from A to B and apply them instantly/in a single step (you may account for drag, coriolis, etc).

With this solution you don't have to wait for the force to propagate across the object during many time steps, and it will behave in a perfectly rigid way. This is what ObiSolver does to calculate inertial forces, and why I suggested using them instead: when the solver moves, it calculates the linear/angular velocities required to move all actors inside with it (accounting for euler, centrifugal and coriolis forces) and applies a controllable percentage of them instantly.

Yeah, this is why I propagate forces along the rod currently, however the previous idea with moving the solver itself is far from good, because if I want to simulate anything else, then those object would move too, plus when rod bends (imagine rod hitting wall, so it bends 90 deg to right) that force would push part of the rod into wall.
But overall, yes it's better to simulate those forces this way than fighting substeps and simulation itself, even if it's not fully "physical".

I'm not really sure what stability has to do with this, could you elaborate on it?

When there are different masses, the rod (that is expected actually) behaves like it was thinner or thicker in some places, but this causes natural propagation to break sagnificantly.
The thing is that even if masses are equal you might encounter problem from attached picture, where the fact how constraints are resolved make some "breaking bends", and this is physical behaviour overall, but rod does not have infinite number of particles/atoms and pushing and pulling can cause those bends to resolve in oscillating way. I guess you can picture what I mean. In reality forces propagate with speed of sound, so this problem does not exist.