No, but I did speak to the owner of that bike. He's put a boatload of time and effort into it, and it shows. Nicer condition than my '75 for sure. I left around 11 and shortly thereafter spent most of the rest of my day attempting to diagnose why the battery was charging at 15.7V (or perhaps even a bit more). Haven't figured it out yet, and all of the usual diagnostics were unsuccessful. All I am left with is the weird separate regulator that Honda used in those years. It's a bad design. A modern-ish MOSFET-based replacement is $130.
Both of the bikes overcharge, but I haven't diagnosed the '77 yet. I know for sure that both bikes have OK (the '75) and really good (the '77, because I just fixed them) stator wire connections. Shrug.
I only saw one CX500 (a personal favorite), and I think I saw two ST1300's. I saw zero ST1100's. I only saw three other "classic" ('75-79) Goldwings. Not nearly as much "interesting" stuff as in years past, sadly.
Anyway, hope you had a lovely day. It was a beautiful day for a ride!