Thank you very much for that hint, Charles. I've just tried APing, and with some rewriting of my script I might be able to use it.
If I fail to make it work, at least you reminded me of the plugin feature in TCC, so maybe I'll just write my own ping6 plugin
Oh, FYI, I ran this on my Windows 10 machine, which is my normal mode. I do sometimes need to run this on a Windows 2012R2 server (network security thing) and when the APING plugin tries to load, I get this error: