You mean, in post #6, where it tells you to type "tail --bytes=+61 Forerunner620_290.rgn > GUPDATE.RGN"
Did you try that?
Ah! You know, I wasn't clear that the person posting meant to literally type that in the terminal. I thought it was just tech-speak instructions that I was supposed to know how to act upon. So ..... I put the file on my desktop, opened terminal, cd Desktop, typed in that string, and it worked. How about that! But the bottom line is the same. I put the new file (and separately tried the one Mark created) into the relevant directory. Some posters said to call it .rgn, some said .gcd; I tried each combination. Each time I copy it over, eject/reboot the watch, and nothing changes. Perhaps I'll remember to bring the watch on my next museum trip (tomorrow) and use our office PC which dual-boots into Windows and Linux.