stacking GCs and other experimentals

Hello, I've seen this done several times and have not figured out how it is done; please let me know if this is a game mechanic- how do I do this?

I've seen people have like 4-5 gcs almost on top of eachother, i've seen 2 experimental battle ships (tempest) stacked so they look like just 1 with 2 guns; how is this done? I've noticed sometimes when units are getting into formation they will seem to walk thru eachother more liberally; but what I've seen looks like the units have been told to move- and their collision box becomes almost nothing.

Any advice or tips on this would be great, I'd especially would like to know if this is not allowed in ranked games.

Check the bottom part for spread move, I believe this is what you want.

thank you very much; this isn't what I am seeing, but it helped me recreate it somewhat. I did some tests with 80 gcs.
If I use spread move alone, the units will still bump into each other- but they do get closer than usual. If I use spread move to clump them up as much as possible, then tell them to get into formation- they will stop bumping into each other and overlap- that is what I see people do, but I can only do it in formations; is there a way to use formation move where all the units go to a single spot?

I also noticed that the units all need to be in the same 'formation' in order to not bump into eachother; I do recall that the game I played where the guy had like 200+ gcs, he never micro'd them and they did all change direction together like it was 1 group of units.

Is there a mod that does this? (allows 'Formation Stacking' where all units are told to go to a single spot (like Spread Move) but they retain their 'Formation Stacking' so they freely overlap.)