I just explained to a Sri Lankan engineering colleague the concept of chain stretching. I told him that 1/8" increase over 12" indicates a stretched chain and a replacement is most likely warranted for optimal performance.

He then asked why you couldn't replace one link with a link that's 7/8" he said that that's what they'd do in Sri Lanka.

That wouldn't work, would it?

That's missing the problem altogether. The problem is less that your chain is too long, than that your chain is too long because your pins are worn. Putting on a 'short link' would shorten the chain back to the correct overall length, but not solve the underlying problem.

Is your colleague a mechanical engineer? Let's hope not.

https://www.sheldonbrown.com/chains.html

No, I can see where that would work if you custom machine the rest of your cogs and chainwheels to accept your inconsistent chain.

The 1/8" over 12 links is just an easy way to measure what is in actuality 1/96" over every link (on average), and the problem is with each link mating with each cog, not a total length.

Remind me to never, ever visit Sri Lanka.

Nothing wrong with visiting, just don't use any of their mechanical appliances: airplanes etc.

Oh and apparently avoid the bicycles too.

Or, you could just measure each individual link, and replace them as needed . . .

It's probably easier to take each cog out individually and enlarge it slightly by cold-forming it with a big mallet on an anvil.