If you nudge your games, 5 inches should be ok, but you need to watch them and adjust when necessary , 1” is asking for trouble

Right now mine are at 2.5 inches. Too much furniture in the game room. My tilts are set loose, the games get nudged. I don't have any problems with interference. I pull the machines out of line for service.
I did have to put rubber under Earthshakers feet as it did move around some on the hardwood floor.

Heads touching is too close. Other than that it’s personal preference. I have league and tournaments a lot so I keep them further apart. Like 6-8” between the heads at least. 1.5’ between the buttons at least.

I used to have mine all jammed together with about an inch between heads, but that's a clusterfk. If they're that close together, it's time to get rid of some.

You need them far enough apart to get your fat ass between them to access the head.

If they are too close, and one is wired backwards, you will complete the circuit, and your crotch will be zapped.

So that’s what my wife was doing, she mumbled somethn about “better than a spin cycle”

I like my players to be able to feel the heat from the hands of the player next to them. For some reason I like them feeling a bit awkward so I can beat them.

Yes. You want to be able to check fuses and change batteries without moving games around.
Width required varies from one ass to another.

Mine are like half an inch apart because space is tight. It’s fine for me. I nudge but never enough to move the damn machine around.

Now there you go, it looks like you solved your own problem, you can have two more pins now. One in the main row by tightening them all together and the other in the spot you have the new game in now. Stack them like cord wood I always say.......LOL.

John