A few notes:
West Chicago presence was awesome. Go on their Facebook page (if you do that) and comment that it was. No problem with parking, no problem with shuttles, no problem with access, free iced bottled water for everybody (and no running out!), properly managed lines for the attractions, etc.
Thousands and thousands of people, most of whom were not 'card-carrying railfan' types. Constant crowd walking both ways across the bridge, independent of the shuttle buses. The event ran until 4:00 but new people weren't admitted starting a few minutes after 3. Lines for attractions were hopelessly long, and isn't that a wonderful thing, considering.
Crew was there and stayed accessible. Austin Barker gave me a rundown on the Dickens-Barker burner, the problem with the right-front packing, and the current state of Green Velvet oil availability; the engine is burning waste motor oil, apparently well enough 'prepared' that there is no firing difficulty with it. Ed Dickens for some reason appeared to be avoiding me, but he was the soul of civility to a VERY wide range of people, some of whom were ... difficult. (He has a Weimaraner, he likes tugboats, he signs hats in green because that's the color pen he uses for inspections...)
It turns out the boiler pressure has to be kept above around 200psi, so they periodically blow back up all the way to 300psi (not some lower layover pressure). How they were doing this earlier in the day was fascinating if you knew what you were looking at... there is what I can only describe as a piece of 2x4 covered with tinfoil that is stuck in the primary-air inlet, and when that is removed natural circulation through the stack is enough to allow the burner to be fired on high turndown, with no visible haze (you can see the heat ripples). I did not observe the rate of pressure rise, but it would logically be relatively slow. At about 2:00 they appeared to need a bit of additional blowing up and the blower was engaged at low mass flow; this gave a bit of visible haze but no particular 'lifting' or smoke ejection; I only saw one of the pops lift once, not for very long (presumably they used injection to quiet this quickly). Ed quietly joked at one point 'don't tell, but it's all a fake; we make smoke to blow out but we push the engine around' ... don't you be-lieve it!
Whistling took place only a couple of times per hour, and then only at relatively low volume. I suspect this was a condition imposed, perhaps Sunday only, by West Chicago, but a fairly substantial range of those I observed were complaining about the lack of whistle sound.
A bit of bad news that is probably not much of a surprise: 3985 will be 'stored serviceable' but there are no immediate plans to run it through the QC rebuild process at this time, either now or for a mid-2020s timeframe. Apparently the plan is now to run the Big Boy indefinitely as the 'second locomotive' -- Ed noted specifically that California will be on the agenda later this year, which may be no surprise to those following the tour postings but is a confirmation that the engine can go lots of places and will be used to go lots of places on the UP system.
It's astounding how most people seem to think steam locomotives work. A very large number of people asking questions seemed to think the oil was mixed with the water in the tender, and this mixture was burned directly to generate steam.