ok, i finally found the time to make a guide / tutorial.
So here’s how i got it working
First you’ll see the final setup, then i will explain everything i did, step by step
Step #1 – Simulation Space
I choose the option «World» due to someone was saying it won’t work otherwise ingame.
Step #2 – Chain
I checked this option to be able to create a simulation on multiple, connected bones.
I’ve set the third bone as starting point fort he simulation, because i didnt want the other Bones to move and distort the mesh. As «chain end» i simply selected the last bone of my chain.
Step #3 – Box Extends
This is the most important one to control the simulation behavior. The shape of this boxes defines the «weight » of the bones which directly has influence on the flexibility.
A chain with 5kg per chain-link will behave differently than a small one with just a few gram per chain-link.
For this i can’t really give you advice. Its just try and error.
Step #4 – Local Joint Offset
This one works directly with the Box extends. It sets the center-position of your simulation volume. You HAVE TO give an offset, otherwise your chain will swing wildly in all directions because your center oft he volume is right at the Bone joint. I’ve set it in the local Y axis and moved it a little bit over the center of the corresponding bone.
Step #5 – Advanced: Linear-/ Angular Damping
I can’t really say anything about those. The behavior just felt a little bit better with those two set.
To be able to change those values, you have to check «Override Linear / Angular Damping» Options, which are just below the Values.
Steop #6 – Constraints
In here you can define some limits for Linear and angluar Movement per Bone.
i limited the angular movement for each bone from -30 up to +30 degrees. A single bone won’t be able to rotate past this value
Also i’ve set the Y-Axis as Twist axis.
Step #7 – Collision
Now to the collisions. The collision wont work with your physics asset or other blocking volumes you’ve set inside your skeletal mesh.
If you are following my steps, you also might have noticed, a bouncy/jittery movement, which goes wild sometimes while playing.
Well, i couldn’t get rid of it completely, but at least i could get rid of the massive stretching.
Step #7.1 – Collsition Type
As collision type i choose a custom sphere with a collision radius of 3.0, nothing to big, because my asset is very thin.
Step #7.2 – Spherical Limits
With the spherical Limits we can define either, if it is INSIDE a sphere and can’t get out of it or if it is outside a sphere and cant «penetrate» it.
I created 4 spheres, the first one set to «inner» with the root bone as center of the sphere (the big one). This prevents the asset from stretching, so i’ve set the radius to be just a little bit over the end of the last bone in the chain.
The other three Spheres are all set to «outer» and are all the same, and placed just below each other.
With those i fake the collision with the leg right next to my asset. This won’t adapt to the leg’s movement while running, but at least for me, this worked well enough. The radius of those spheres was try and error, until i had it more or less as desired.
Step #7.3 – Planar limits
Planar limits works like a blocking volume but just as plane. I used it to prevent my asset from swingig above a specific point, in my case above the hips.
Conclusion
As i said, i couldn’t get rid of the small bouncing and sometimes, mostly when i begin to run, the asset is for a short amount of time jittery, but mostly this vanishes.
There might be a better solution than mine, a better way to set it up, to get rid of the bouncing completely, but i wasn’t able to find out.
I still hope my solution helps other ones and saves you some time 
