One other thing (I'm sure you already know this). Traditional approaches to control charts is based on normality of data and bell curve. Steve bases his approach on... I'm not even going to attempt his name.. inequality. Not sure how detailed/deep you're going with this. If you're pushing to publish this, it might be worth mentioning.
It may also be worth noting that Dr. Shewhart tested his scheme with a 1930's random number generator - numbered hat tokens in a bowl. He made up three sets - normal, rectangular, and triangular distributions. The random numbers he ended up drawing are laboriously reprinted in Economic Control of Quality . . .