I'm so glad this proved to be of interest to others.As for experiments - watch this space. It will take a bit of time to figure out how to configure something safe and robust enough to stand any chance of positive results. Also, some large coils will be required, both for a low frequency tuned circuit, and to "choke" the arc current supply.
Another approach that has rattled loose in my head while contemplating this is a more delicate negative resistance oscillator I remember (and re-found, see link) using a point contact with oxidised zinc:
www.sparkbangbuzz.com/els/zincosc-el.htm
The results obtained by the experimenter showed capability into the MHz frequency range. They were able to reproduce the effect with a variety of objects and materials. Not sure if this could reach 22m, but the idea of an entirely pre-electronic HiFER has a certain allure.