Traditionally, L6 engines of any type have excellent (but not "perfect") balance, with minimal vibration.
They all have counterweights, yet many comments suggest that "they don't need to be balanced", when of course they already are.
My question: assuming the engine will see severe service, any reasonable method to keep the lower end together is worth examining.
The question: has anyone had any L6 balanced? What was done, and why?

[please: don't cut-n-paste from Wikipedia, we all know what it says]

Thanks!