Stacking the nonstackable

[LABHOUSE]

Works with any engine being on top, reusable:

Reusable, but does not work with all engines:

↑Uses the docking port that cannot dock.

Sorry if this is in the wrong section.

[Superfluous J]

I've tried similar in the past but never got them even close to balanced.

[GusTurbo]

Not sure I understand what's happening here. What does the claw do?

[LABHOUSE]

The claw can connect another stage beneath the engine.

[Rfmeijboom]

This is my solution to the unstackable engines:

Full functionality, no extra parts needed, only creative use of the offset and rotation options.

Craft file here: (Un)stackable.craft

[Foxster]

Cubic Octagonal Struts attached to the bottom of most things like those engines too...

[Rfmeijboom]

The cubic octagonal strut will also work, but you have a weaker joint and it can be tricky to align them exactly in the middle.

[Azimech]

Instead of the cubic strut, just use the flat radial connector thingie. Can withstand the force of the biggest engine.

Centering: go radial and choose 3. Align them so they look as one. Use angle snap so it will mount straight. Back to single, mount. Done.