so, been having issues with the "core ship" not being kept as the core after the split, but i think i have it figured it out..
first off, what the core ship is when you build and what it is after you spawn from your library after saving is differant.
here is two ship designs, one of which finally always has the mother ship as the "core" after the minis are launched.
this one always has the top left child become the "core" after the split instead of the mothership.
This one the children are never considered the "core" after the split anytime i spawn it in from the Library.
the difference is that i added a cockpit to the top corner of the mothership, i added it there when i noticed that it was always the top left most ship in any of my swarm builds that seemed to be the core..
it can be gathered that the "core" is considered any part connected to the top left most cockpit.
replacing the same tile with anything else does not alter which ship becomes the "core" however adding the cockpit to that corner changes which becomes the core.
i dont know if this is the for sure reality of how the "core" gets determined, but for me it does seem that where the top left most cockpit is located will be considered where the core of the entire build is when enough damage is done.
to further test the concept i did this build
once i save the build, and spawned a new one of it in, the tiny ship that separates on the absolute top left becomes the "core".
when you build a craft, this is initally the first cockpit you place. when you save and then spawn a build in from the library, this top left rule seems to apply..