Large modular (docking ports) rockets... springy?

[AlexMBrennan]

I was trying to build a rocket with a large base and 4x nuclear engines (attached via a quad adapter), and noticed that I can't have any stages attached below them because the unique lateral ejection of the launch covers tends to blow at least two of LV-Ns.

I figured that the easiest solution would be to take the bottom half of the intended rocket design, flip it around, mount it on a lifter and dock it with the top half of the rocket in orbit... however, I noticed that this results in the docking ports very noticeably compressing/expanding when adjusting the throttle. The relevant section (with infinite fuel to reproduce the state) looks like this:

I never noticed this behaviour before with docked modules - is that the intended behaviour? Barring mods (quantum struts?), is there any solution other than not using docking ports in this way?

[i ended up taking out all the docking ports and launching in one go - I got 1600t monster to get a 160t rocket to orbit)

Lander will be docked to the nose later (because it will be facing the opposite way it tends to screw up staging and instruments/navball)]

[vexx32]

I believe it is fairly common to mount 1m docking ports onto tri- or quad-couplers and dock them all to corresponding arrangements of docking ports on the target vessel in order to get a good amount of joint strength.

[Kasuha]

I was trying to build a rocket with a large base and 4x nuclear engines (attached via a quad adapter), and noticed that I can't have any stages attached below them because the unique lateral ejection of the launch covers tends to blow at least two of LV-Ns.

You can, if you make sure you rotate LV-Ns in VAB so their shrouds collide with each other rather than with engines.

I never noticed this behaviour before with docked modules - is that the intended behaviour?

That's not property of docking ports, it's property of joints between parts. Docking ports are rather thin so the displacement on joints is more visible there. For liftoff it's a good idea to put some struts around. If you have this problem in space then your ship has too much thrust.

[Roxette]

Kerbal Joint Reinforcement/ is a worthwhile investment. The senior docking port in particular is prone to wander about under thrust loading.

[Kasuha]

If you check the ship below, there is a whole lot of docking ports in between each two parts. 10 total, not counting one more at each end. Yet it was no problem to lift it when strutted properly. and by properly I don't mean large amount. No reinforcements were necessary.