So ten years later, to the month, here I am doing this thermostat job again: -
https://xoutpost.com/1079662-post7235.html
Only difference is that with ten years of inflation, a Chinese part costs $100, a Mahle/Behr part costs $150 (ex. Latvia) and a genuine part costs around $400. So I went with this...
(That and I broke off the radiator drain bolt - of course!!

)
Engine now running at the proper temp again. Time will tell...