I have a 6100 with the piggy back crystal for 40MHz bus + a Sonnet G3 card (I think it selects 220MHZ when the bus is 40MHz). Haven't booted it in a while but it worked great for years in that configuration.
Just saw this linked somewhere else, looks very cool:
https://henlin.net/2022/10/02/Introducing-FocusedEdit-for-classic-Macintosh/
"FocusedEdit is a new text editor for classic Macintosh computers (running System 2 through MacOS 9.2.2) and the CoprocessorJS library that allows shared...