This wonderful conversation reminds me of how much I miss Shrink. Hope he is ok.
The most important ingredient in pulling shots is truly caring how the shot tastes. I go back to a post over in the Caffe Mocha thread....it all depends on priorities. To some, convenience is the preeminent concern. That is why SB flourishes by selling what is really not very good coffee, and a complete inability to, god forbid, pull a shot of espresso.
This is why, for example, I know to a metaphysical degree of certainty that the shots y'all pull are in quality far beyond what any push-button barista has any hope of pulling. You truly care. That is the difference.
The fun and eternally frustrating thing about The God Shot is that as soon as you pull one, your standards go up and the next one becomes even harder to pull. The same is true as a general standard. Truly caring pushes you to improve, and this year's acceptable shot becomes next year's throw away. A comment about Sisyphus probably should come next.....
I hope that my fanaticism about taste never comes off as, well, arrogance or bumptiousness. It's just me.
On the other hand, if you hurry up and buy, we can argue for hours on end whether the pre-infusion temperature should be 202.5 or 202.6. It matters!
Back to the steam wand for a second. SG, do you know whether the light on your machine, in the "on" state, indicates that the heating element is on, or that the boiler has achieved a certain pressure?
Smaller machines can struggle with steam, but your machines are high quality and I would be shocked if they cannot produce enough steam to make a large white coffee. How recently have you descaled?
I will keep my eyes open for a steam wand upgrade for your machines.
One comment on tapping the PF; this used to be the standard way that was taught (and here I feel like Clint Eastwood as the old man: "Get off my lawn!"). But, tapping can promote channeling, so it was replaced a few years ago (among the bloggers) by something called the Weiss Distribution Technique, which involves stirring the grounds with a needle before tamping. If you Google "WDT espresso" you will find many furious arguments on the subjects of tapping.....
My vote is: do what tastes good.